In each of the following problems, decide whether the given subset W of the vector space V is or is not a subspace of V. If not, identify at least one requirement that is not satisfied. Assume that the standard definitions of addition and scalar multiplication hold.
(a) V = P2, W = {p(t) | degree of p(t) = 2}
(b) V = C[0,1], W = {f(t) | f(0) = f(1) = 0}
(c) V = C[a, b], W = {f(t) | lim(a→b)∫ f(t) dt = 0}
(d) V = C²[0,1], W= {f(t) | f" +2f = 4}