Which of the following subsets of P2 are subspaces of P2? A. {p(t) | p(3)=0} B. {p(t) | p(−t)=−p(t) for all t} C. {p(t) | p(0)=3} D. {p(t) | p′(t)+8p(t)+5=0} E. {p(t) | ∫60p(t)dt=0} F. {p(t) | p′(t) is constant }