Let R5[t] be the vector space of all polynomials in t of degree 4 or less with real coefficients. Which of the following subsets are subspaces?

Question

I know how to test if something is a subspaces, just not sure how to do it with for these polynomial equations.

a.) {p(t)|the constant term of p(t) is 1}

e.) {p(t)|the degree of p(t) is 3}