cset_science_mc_practice_brainscape

Question 1

[MC-1] Which of the following processes involves a chemical change?

A. Ice cubes melting in a glass of water
B. Iron forming rust when exposed to moisture and air
C. Salt dissolving in water to make a saline solution
D. Steam condensing on a cold window

Answer 1

B. Iron forming rust

Rusting is a CHEMICAL change because new bonds form—iron combines with oxygen to create iron oxide (Fe₂O₃). Melting, dissolving, and condensing are physical changes (same molecules, different arrangement).

Question 2

[MC-2] Which pair of elements would be expected to have the most similar chemical properties?

A. Na and Mg
B. S and Cl
C. Li and Na
D. Si and P

Answer 2

C. Li and Na

Elements in the same COLUMN (group) have similar properties because they have the same number of valence electrons. Li and Na are both in Group 1 (alkali metals). Na/Mg, S/Cl, and Si/P are in the same row but different columns.

Question 3

[MC-3] A student tests four substances with pH paper and records: W=pH 3, X=pH 7, Y=pH 9, Z=pH 12. Which substance is most acidic?

A. Substance W
B. Substance X
C. Substance Y
D. Substance Z

Answer 3

A. Substance W (pH 3)

Lower pH = more acidic. The pH scale runs 0-14, with 7 being neutral. Substance W at pH 3 is acidic; X is neutral; Y and Z are basic/alkaline.

Question 4

[MC-4] Oxygen-16 and Oxygen-18 are both isotopes of oxygen with atomic number 8. How do these isotopes differ?

A. Oxygen-18 has two more protons than Oxygen-16
B. Oxygen-18 has two more neutrons than Oxygen-16
C. Oxygen-18 has two more electrons than Oxygen-16
D. Oxygen-18 has two fewer neutrons than Oxygen-16

Answer 4

B. Oxygen-18 has two more neutrons

Isotopes have the same number of protons (which defines the element) but different numbers of neutrons. O-16: 8 protons + 8 neutrons. O-18: 8 protons + 10 neutrons.

Question 5

[MC-5] Which of the following correctly describes the properties of an electron?

A. Mass of approximately 1 amu, negative charge, located in the nucleus
B. Mass of approximately 1 amu, no charge, located in the nucleus
C. Mass much less than 1 amu, negative charge, located outside the nucleus
D. Mass much less than 1 amu, positive charge, located outside the nucleus

Answer 5

C. Mass much less than 1 amu, negative charge, located outside the nucleus

Electrons have negligible mass (~1/1836 amu), negative charge, and orbit the nucleus. A describes nothing real; B describes a neutron (but wrong location); D has wrong charge.

Question 6

[MC-6] A pencil placed in a glass of water appears bent at the water’s surface. This phenomenon is best explained by:

A. The absorption of light by water molecules
B. The reflection of light off the water’s surface
C. The refraction of light as it passes between air and water
D. The diffraction of light around the edge of the pencil

Answer 6

C. The refraction of light as it passes between air and water

Refraction is the bending of light when it passes between media of different densities. Light slows down in water, causing it to bend and making the pencil appear displaced.

Question 7

[MC-7] A swimmer pushes backward against the water with her hands and moves forward through the pool. This is best explained by:

A. Newton’s First Law—the swimmer’s body tends to remain in motion
B. Newton’s Second Law—force equals mass times acceleration
C. Newton’s Third Law—the water exerts an equal and opposite force on the swimmer
D. The law of conservation of energy

Answer 7

C. Newton’s Third Law—the water exerts an equal and opposite force

The swimmer pushes water BACKWARD (action); the water pushes the swimmer FORWARD (reaction). These are equal and opposite forces acting on different objects—the definition of Newton’s Third Law.

Question 8

[MC-8] A metal spoon at 25°C feels colder to the touch than a wooden spoon at 25°C. This is best explained by:

A. The metal spoon has a lower temperature than the wooden spoon
B. The metal spoon has less thermal energy than the wooden spoon
C. The metal spoon conducts heat away from your hand faster than wood does
D. The wooden spoon absorbs more heat from your hand

Answer 8

C. The metal spoon conducts heat away from your hand faster

Both spoons are at the same temperature (25°C). Metal is a better thermal conductor, so it transfers heat FROM your hand more quickly, making it feel colder. This is about conductivity, not temperature or thermal energy.

Question 9

[MC-9] A skydiver accelerates downward but eventually reaches constant ‘terminal velocity.’ Which graph best shows speed versus time?

A. A straight line with constant positive slope
B. A curve that rises steeply at first then levels off horizontal
C. A straight horizontal line
D. A curve that starts horizontal then rises steeply

Answer 9

B. A curve that rises steeply at first then levels off horizontal

Initially, gravity accelerates the skydiver (speed increases rapidly). As speed increases, air resistance increases until it equals gravity—then acceleration stops and speed becomes constant (terminal velocity).

Question 10

[MC-10] A celery stalk placed in red dye water shows red streaks. If then placed in heavily salted water for 24 hours, what will most likely occur?

A. Celery becomes crisp and turgid with red color fading
B. Celery becomes limp and wilted with red color remaining
C. Celery remains unchanged with red color intensifying
D. Celery becomes crisp with red color intensifying

Answer 10

B. Celery becomes limp and wilted with red color remaining

The dye traveled up the xylem and remains in the tissue. The salt creates an osmotic gradient—water leaves the cells toward the higher solute concentration outside, causing wilting. Two separate effects: color stays, turgor is lost.

Question 11

[MC-11] A patient has weakened left ventricle pumping force. Which body systems would be MOST directly affected?

A. Only the respiratory system because lungs receive blood from the left ventricle
B. Only the digestive system because it requires the most blood flow
C. Most organs throughout the body because the left ventricle pumps into systemic circulation
D. Only the brain because it is located above the heart

Answer 11

C. Most organs throughout the body because the left ventricle pumps into systemic circulation

The left ventricle pumps oxygenated blood to the ENTIRE body (systemic circulation). The RIGHT ventricle pumps to the lungs. A weakened left ventricle affects all organs and tissues.

Question 12

[MC-12] Carbon atoms are central to proteins, carbohydrates, lipids, and nucleic acids primarily because carbon:

A. Is the most abundant element in living organisms
B. Can form four covalent bonds with many different elements
C. Has the lowest atomic mass of elements in biological molecules
D. Can easily gain or lose electrons to form ionic bonds

Answer 12

B. Can form four covalent bonds with many different elements

Carbon’s ability to form 4 covalent bonds allows it to create long chains, branches, and rings—the complex structures needed for biological molecules. Carbon is NOT the most abundant element (oxygen and hydrogen are more common by mass).

Question 13

[MC-13] Clownfish live among sea anemone tentacles, protected from predators and bringing food to the anemone. The anemone is not harmed. This relationship is:

A. Parasitism
B. Commensalism
C. Mutualism
D. Predation

Answer 13

C. Mutualism

Both species benefit: clownfish get protection; anemone gets food. Mutualism = +/+. If only the clownfish benefited and the anemone was unaffected, it would be commensalism (+/0).

Question 14

[MC-14] Grass captures 10,000 kcal from sunlight. How much energy is available to a hawk that eats a snake that eats a mouse that eats the grass?

A. 10 kilocalories
B. 100 kilocalories
C. 1,000 kilocalories
D. 2,500 kilocalories

Answer 14

A. 10 kilocalories

Apply the 10% rule at each trophic level:
Grass: 10,000 → Mouse: 1,000 → Snake: 100 → Hawk: 10 kcal

~90% of energy is lost as heat at each level through metabolism.

Question 15

[MC-15] Different plant species grow at different mountain elevations: oaks low, pines middle, shrubs at summit. Which factor most likely explains this?

A. Soil pH
B. Carbon dioxide concentration
C. Temperature
D. Oxygen availability

Answer 15

C. Temperature

Temperature decreases predictably with elevation (~3.5°F per 1000 ft). This creates distinct temperature zones that determine which species can survive. CO₂ and O₂ don’t vary enough over this scale to be limiting factors.

Question 16

[MC-16] In stable, resource-rich environments, asexual reproduction would be advantageous because:

A. It produces offspring with greater genetic diversity
B. It allows rapid population growth without requiring a mate
C. It ensures offspring will have new combinations of alleles
D. It increases the chance of beneficial mutations

Answer 16

B. It allows rapid population growth without requiring a mate

Asexual reproduction is FAST—no mate needed, all individuals can reproduce. When conditions are good, rapid replication is advantageous. Options A, C, and D describe advantages of SEXUAL reproduction (genetic diversity).

Question 17

[MC-17] Root tip cells divide to grow the root; flower cells divide to make pollen. Which correctly compares these?

A. Both result in cells with same chromosome number as parent
B. Both result in cells with half the chromosome number
C. Root division maintains chromosome number; pollen formation reduces it by half
D. Root division reduces chromosome number; pollen formation maintains it

Answer 17

C. Root division maintains chromosome number; pollen formation reduces it by half

Root growth = mitosis (2n → 2n, same chromosome number). Pollen formation = meiosis (2n → n, half the chromosomes for gamete formation).

Question 18

[MC-18] A plant placed on its side in a dark room has its stem bend upward after one week. This growth is primarily a response to:

A. The plant’s internal biological clock
B. Gravity
C. Touch stimulation from the pot
D. Temperature differences

Answer 18

B. Gravity

This is gravitropism (geotropism)—response to gravity. The stem grows AWAY from gravity (negative gravitropism). Since there’s no light in the room, it cannot be phototropism. The plant detects gravity using statoliths in cells.

Question 19

[MC-19] Based on a diagram showing new moon position (Moon between Earth and Sun), which statement is true?

A. A new moon rises at approximately the same time as the sun
B. A new moon is visible high in the sky at midnight
C. The new moon appears fully illuminated from Earth
D. A new moon can only occur during a solar eclipse

Answer 19

A. A new moon rises at approximately the same time as the sun

During new moon, the Moon is between Earth and Sun, so they rise and set together. The dark side faces Earth (not illuminated from our view). Solar eclipses CAN occur during new moon but don’t happen every time.

Question 20

[MC-20] Which best describes the location of our solar system within the Milky Way galaxy?

A. At the center of the galaxy near the galactic core
B. In one of the spiral arms about two-thirds of the way out from the center
C. In a spherical halo surrounding the main disk
D. At the outer edge beyond the spiral arms

Answer 20

B. In one of the spiral arms about two-thirds of the way out from the center

Our solar system is in the Orion Arm (or Orion Spur), approximately 26,000 light-years from the galactic center—roughly two-thirds of the way from center to edge.

Question 21

[MC-21] Buildings on bedrock sustain less earthquake damage than those on loose sediment primarily because:

A. Bedrock absorbs seismic energy while loose sediment reflects it
B. Seismic waves travel faster through bedrock giving less shaking time
C. Loose sediment amplifies ground shaking compared to solid bedrock
D. Buildings on bedrock are typically older and built stronger

Answer 21

C. Loose sediment amplifies ground shaking compared to solid bedrock

Loose, unconsolidated sediment amplifies seismic waves. In extreme cases, saturated sediment can liquefy. This is why the 1989 Loma Prieta earthquake caused more damage near San Francisco Bay (built on fill) than on bedrock.

Question 22

[MC-22] A meteorologist uses a device measuring force exerted by the atmosphere on a surface. This device is called a:

A. Hygrometer
B. Barometer
C. Anemometer
D. Thermometer

Answer 22

B. Barometer

Barometer measures atmospheric/air pressure. Hygrometer = humidity. Anemometer = wind speed. Thermometer = temperature.

Question 23

[MC-23] On a hot summer afternoon a thunderstorm develops over a valley. Which best describes conditions leading to this?

A. Cool air near ground was heated by radiation from clouds
B. Warm moist air near surface rose rapidly, cooled, and condensed to form clouds
C. Strong winds picked up dust particles that seeded cloud formation
D. Cold air from high pressure pushed warm air aside

Answer 23

B. Warm moist air near surface rose rapidly, cooled, and condensed to form clouds

Convective thunderstorms form when surface heating causes warm, moist air to rise. As it rises, it cools (adiabatic cooling), water vapor condenses, and cumulonimbus clouds form. The key mechanism is RISING warm air.

Question 24

[MC-24] Location A has 2m tidal range; narrow bay Location B (50km away) has 8m range. The most likely explanation is:

A. Location B is closer to the moon during high tide
B. Location B has stronger winds pushing water higher
C. The narrow shape of the bay concentrates tidal waters
D. Water at Location B is saltier

Answer 24

C. The narrow shape of the bay concentrates tidal waters

The funnel effect: as tidal water enters a narrowing bay, it has nowhere to go but UP. The Bay of Fundy has 50+ foot tides due to this effect. The 50km distance is too small for moon proximity to matter.

Question 25

[MC-25] Lake Bonneville was freshwater during Ice Age; Great Salt Lake today is extremely salty. Which best explains this? A. Underground volcanic activity released mineral salts B. Climate change caused rivers to carry more dissolved salts C. The lake shrank and lost its outlet, concentrating salts through evaporation D. Salt was deposited by ancient ocean waters

Answer 25

C. The lake shrank and lost its outlet, concentrating salts through evaporation As climate warmed, evaporation exceeded inflow. The lake lost its outlet to the ocean. With no way for dissolved salts to leave, evaporation concentrated them over thousands of years. ALL water contains trace salts—closed basins concentrate them.

Question 26

[MC-26] A scientist studying air pollution effects on respiratory health needs primary data. Which would serve as a PRIMARY source? A. A newspaper article describing pollution health effects in other cities B. A government report summarizing air quality regulations nationwide C. Direct measurements of pollution levels and lung function tests from study participants D. A textbook chapter explaining biological mechanisms of respiratory disease

Answer 26

C. Direct measurements of pollution levels and lung function tests from study participants Primary sources are ORIGINAL, FIRST-HAND data from YOUR specific study. Direct measurements you collect are primary. Articles, reports, and textbooks are secondary sources—someone else's interpretation or data from other contexts.

Question 27

[MC-27] A beetle population on dark bark became predominantly dark-colored over generations. Which best explains this? A. Individual beetles darkened their coloring to match bark and passed this to offspring B. Dark beetles were harder for predators to see, survived more, and reproduced more C. Beetles needed to be darker to survive so mutations for dark color occurred D. Bark color caused beetles' genes to mutate toward darker coloration

Answer 27

B. Dark beetles were harder for predators to see, survived more, and reproduced more This is correct Darwinian natural selection: variation existed, selection pressure favored dark beetles, they reproduced more, population changed over generations. Options A, C, and D are all LAMARCKIAN errors—traits don't arise because they're needed.

Question 28

[MC-28] A student says: 'Bacteria develop resistance because they need to survive.' What is the primary error? A. Bacteria cannot pass traits to offspring B. Antibiotics do not actually kill bacteria C. Resistance mutations arise randomly, not in response to need D. Only some bacteria are capable of developing resistance

Answer 28

C. Resistance mutations arise randomly, not in response to need This is the key anti-Lamarckian concept: mutations are RANDOM with respect to fitness. Resistance genes existed BEFORE antibiotic exposure in some bacteria. The antibiotic didn't cause the mutation—it just selected for pre-existing resistant individuals.

Question 29

[MC-29] Which statement is consistent with Darwin's theory of natural selection? A. Organisms develop new traits because they need them to survive B. Mutations occur more frequently when they would be beneficial C. Individuals with traits that improve survival tend to leave more offspring D. Species consciously adapt their features to match their environment

Answer 29

C. Individuals with traits that improve survival tend to leave more offspring This is the core principle: differential reproductive success based on heritable variation. Options A, B, and D all imply purpose, need, or consciousness in evolution—all incorrect Lamarckian thinking.

Question 30

[MC-30] Rabbits with brown and white coats live in an area. Permanent snow arrives. According to natural selection: A. Brown rabbits will gradually turn white over their lifetimes B. Rabbits will produce more white offspring because white fur is now needed C. The proportion of white rabbits will increase over generations as they survive better D. Mutations for white fur will occur more frequently due to the snow

Answer 30

C. The proportion of white rabbits will increase over generations as they survive better Selection acts on EXISTING variation. White rabbits already exist; they'll now survive better (camouflage), reproduce more, and the population will shift. Rabbits don't turn white (A), don't produce offspring 'because needed' (B), and mutations don't increase when beneficial (D).

Question 31

[MC-31] Four horizontal sedimentary layers are undisturbed. Which layer is oldest? A. The top layer B. The second layer from the top C. The second layer from the bottom D. The bottom layer

Answer 31

D. The bottom layer Principle of superposition: in undisturbed sedimentary sequences, the oldest layers are at the bottom, youngest at top. Layers are deposited sequentially over time.

Question 32

[MC-32] Three horizontal sedimentary layers are cut by a diagonal igneous dike. According to cross-cutting relationships: A. The igneous dike is older than all three sedimentary layers B. The igneous dike is younger than all three sedimentary layers C. The dike and layers formed at the same time D. The age relationship cannot be determined

Answer 32

B. The igneous dike is younger than all three sedimentary layers Principle of cross-cutting relationships: any feature that cuts through rocks must be YOUNGER than the rocks it cuts. The dike couldn't cut through layers that didn't exist yet.

Question 33

[MC-33] The boundary between two rock layers is irregular/wavy and the lower layer has portions missing. This suggests: A. The two layers were deposited simultaneously B. Erosion occurred before the upper layer was deposited C. An earthquake tilted the layers after deposition D. The lower layer was deposited in deeper water

Answer 33

B. Erosion occurred before the upper layer was deposited An irregular contact with missing material indicates an unconformity—a period of erosion between depositions. The lower layer was partially worn away before the upper layer was deposited on top.

Question 34

[MC-34] A fault cuts through the bottom three layers but NOT the top two. This indicates the fault: A. Is older than all five layers B. Formed between the deposition of the third and fourth layers C. Is younger than all five layers D. Formed at the same time as the third layer

Answer 34

B. Formed between the deposition of the third and fourth layers The fault cuts layers 1-3 (so it's younger than them) but doesn't cut layers 4-5 (so it's older than them). It must have formed after layer 3 but before layer 4 was deposited.

Question 35

[MC-35] Which is an example of refraction? A. Seeing your reflection in a calm lake B. A prism separating white light into a spectrum of colors C. A shadow forming behind an opaque object D. Light being absorbed by a black surface

Answer 35

B. A prism separating white light into a spectrum of colors A prism refracts (bends) light, and different wavelengths bend different amounts, separating white light into colors. A = reflection. C = blocking light. D = absorption.

Question 36

[MC-36] A rocket launches by expelling hot gases downward. According to Newton's Third Law, the rocket rises because: A. Hot gases push against ground, and ground pushes rocket up B. Rocket pushes gases downward, and gases push rocket upward C. Rocket's engines push the rocket upward directly D. Gravity temporarily reverses near hot exhaust

Answer 36

B. Rocket pushes gases downward, and gases push rocket upward Newton's Third Law requires identifying BOTH forces on DIFFERENT objects. The rocket exerts force on gases (pushing down); gases exert equal/opposite force on rocket (pushing up). Rockets work in space where there's no ground—A is wrong.

Question 37

[MC-37] Cup A has 100mL water at 80°C; Cup B has 500mL at 80°C. Which is correct? A. Cup A has more thermal energy because molecules move faster B. Cup B has more thermal energy because it contains more water molecules C. Both have same thermal energy because same temperature D. Cup A has more thermal energy because smaller volumes retain heat better

Answer 37

B. Cup B has more thermal energy because it contains more water molecules Temperature = average kinetic energy per molecule (same for both). Thermal energy = TOTAL kinetic energy of all molecules. More molecules = more total energy, even at the same temperature.

Question 38

[MC-38] A ball thrown straight up. Which graph shows height vs time from throw until return? A. Straight line going up then down (inverted V) B. A parabola (curved arc) that rises then falls C. A horizontal straight line D. A straight line with constant positive slope

Answer 38

B. A parabola (curved arc) that rises then falls Gravity causes constant acceleration, which produces a parabolic trajectory. The ball slows as it rises (decreasing slope), stops momentarily at peak, then speeds up falling (increasing slope). NOT a straight line.

Question 39

[MC-39] Tapeworms in host intestines absorb nutrients; host may become malnourished. This relationship is: A. Mutualism B. Commensalism C. Parasitism D. Predation

Answer 39

C. Parasitism Parasitism = one benefits (+), other is harmed (-). The tapeworm benefits from nutrients; the host is harmed (malnourishment). Unlike predation, the parasite doesn't immediately kill the host.

Question 40

[MC-40] Why are there typically fewer top predators than herbivores in an ecosystem? A. Top predators reproduce more slowly than herbivores B. Less energy is available at higher trophic levels due to energy loss as heat C. Herbivores are better adapted to finding food D. Top predators require less food per individual

Answer 40

B. Less energy is available at higher trophic levels due to energy loss as heat The 10% rule: ~90% of energy at each trophic level is lost through metabolism (released as heat). Less available energy means fewer organisms can be supported at higher levels.

Question 41

[MC-41] A desert receives very little rainfall. Which is most likely the limiting factor for plant growth? A. Carbon dioxide B. Nitrogen C. Water D. Sunlight

Answer 41

C. Water The limiting factor is the resource in shortest supply. In a desert, water is scarce while sunlight is abundant. Plants can't grow without adequate water regardless of other resources.

Question 42

[MC-42] Which process results in daughter cells with half the chromosomes of the parent cell? A. Mitosis B. Binary fission C. Meiosis D. Cytokinesis

Answer 42

C. Meiosis Meiosis produces gametes (sex cells) with half the chromosome number (haploid). Mitosis maintains chromosome number. Binary fission is bacterial division. Cytokinesis is cytoplasm division (part of both mitosis and meiosis).

Question 43

[MC-43] A lunar eclipse occurs when: A. The moon passes between Earth and the sun B. Earth passes between the sun and moon, and moon enters Earth's shadow C. The moon is in its new moon phase D. The moon's orbit takes it behind the sun

Answer 43

B. Earth passes between the sun and moon, and moon enters Earth's shadow Lunar eclipse: Earth blocks sunlight from reaching the moon (occurs during FULL moon). Solar eclipse: moon blocks sunlight from reaching Earth (occurs during NEW moon). A describes a solar eclipse setup.

Question 44

[MC-44] Why doesn't a lunar eclipse occur during every full moon? A. The moon is too far from Earth during most full moons B. The moon's orbit is tilted so it usually passes above or below Earth's shadow C. Earth's shadow is too small to reach the moon most of the time D. The sun's light bends around Earth, usually illuminating the moon

Answer 44

B. The moon's orbit is tilted so it usually passes above or below Earth's shadow The moon's orbit is tilted ~5° relative to Earth's orbit around the sun. Most full moons, the moon passes slightly above or below Earth's shadow. Eclipses only occur when the moon crosses the orbital plane at the right time.

Question 45

[MC-45] Which correctly lists subatomic particles from least to most massive? A. Proton, neutron, electron B. Electron, neutron, proton C. Neutron, proton, electron D. Electron, proton, neutron

Answer 45

D. Electron, proton, neutron Electron: ~1/1836 amu (negligible). Proton: ~1 amu. Neutron: ~1 amu (slightly more than proton). So: electron << proton ≈ neutron.

Question 46

[MC-46] Potassium (K) and Sodium (Na) are in the same column of the periodic table. Which prediction is most reasonable? A. They have the same atomic mass B. They have similar chemical reactivity C. They have the same number of protons D. They are both nonmetals

Answer 46

B. They have similar chemical reactivity Same column = same number of valence electrons = similar chemical properties. Both are alkali metals (Group 1), highly reactive, form +1 ions. They have different atomic masses and different numbers of protons (that's what makes them different elements).

Question 47

[MC-47] Baking soda mixed with vinegar produces bubbles and fizzing. This is evidence of: A. A physical change because substances are simply mixing B. A chemical change because a gas (new substance) is being produced C. A physical change because bubbles are just trapped air D. Neither because original substances remain

Answer 47

B. A chemical change because a gas (new substance) is being produced The bubbles are CO₂ gas—a NEW substance formed by the reaction between sodium bicarbonate and acetic acid. New substance = chemical change. The bubbles aren't trapped air; they're produced by the reaction.

Question 48

[MC-48] A plant in a sealed container shows decreasing CO₂ during a sunny day. This is explained by: A. The plant releasing CO₂ through respiration B. The plant absorbing CO₂ for photosynthesis C. CO₂ escaping through microscopic holes D. Warmth causing CO₂ to dissipate

Answer 48

B. The plant absorbing CO₂ for photosynthesis Photosynthesis uses CO₂ + H₂O + light → glucose + O₂. During the sunny day, photosynthesis exceeds respiration, so net CO₂ decreases. (At night, respiration would dominate and CO₂ would increase.)

Question 49

[MC-49] In the water cycle, which process moves water from ocean to atmosphere? A. Precipitation B. Evaporation C. Runoff D. Condensation

Answer 49

B. Evaporation Evaporation converts liquid water to water vapor, moving it from ocean surface to atmosphere. Condensation is vapor→liquid (forms clouds). Precipitation is water falling. Runoff is water flowing over land.

Question 50

[MC-50] A scientist tests whether new fertilizer increases tomato growth. What would be the best control group? A. Tomato plants with twice the recommended fertilizer B. Tomato plants grown without any fertilizer C. Corn plants grown with the new fertilizer D. Tomato plants in a different location

Answer 50

B. Tomato plants grown without any fertilizer The control group should be identical to the experimental group EXCEPT for the variable being tested (fertilizer). No fertilizer = baseline for comparison. Different amounts, different plants, or different locations introduce confounding variables.

Question 51

[MC-51] An organism is multicellular, cannot make its own food, and can move. It most likely belongs to kingdom: A. Plantae B. Fungi C. Animalia D. Protista

Answer 51

C. Animalia Multicellular + heterotrophic (can't make own food) + motile = animal. Plants are autotrophic (photosynthesis). Fungi are heterotrophic but generally non-motile and absorb nutrients. Protists are mostly unicellular.

Question 52

[MC-52] Mice with genes for better winter food-finding exist in a population. Over many generations, what is most likely? A. All mice will develop better food-finding during their lifetimes B. Mice with better food-finding genes will become more common in the population C. Mice will consciously pass on food-finding skills to offspring D. Mutations for better food-finding will stop once common

Answer 52

B. Mice with better food-finding genes will become more common in the population Natural selection: mice with advantageous genes survive better, reproduce more, and pass those genes to offspring. Over generations, the beneficial allele increases in frequency. A and C are Lamarckian errors; D misunderstands mutation.