Which of the following subsets of p2p2 are subspaces of p2p2? (p2p2 denotes the set of polynomials of degree 2 or less.) a. {p(t) | p′(t)+8p(t)+6=0}{p(t) | p′(t)+8p(t)+6=0} b. {p(t) | p′(t){p(t) | p′(t) is constant }} c. {p(t) | p′(6)=p(3)}{p(t) | p′(6)=p(3)} d. {p(t) | p(0)=3}{p(t) | p(0)=3} e. {p(t) | ∫70p(t)dt=0}{p(t) | ∫07p(t)dt=0} f. {p(t) | p(−t)=p(t){p(t) | p(−t)=p(t) for all t}t}