What is a basis?
A basis is a set of vectors that are used to express the coordinates of vectors located in a given vector space.
A larger set would include a dependent vector.
What happens when we linearly combine the vectors of a basis?
The combination can be 0 only with all 0 coefficients, since the vectors in a basis are independent.
How can we know the dimension of the vector space?
By looking at the number of vectors in the basis.