Let G be a pseudorandom generator. In each of the following cases, say whether G' is necessarily a pseudorandom generator. If yes, give a proof; if not, show a counterexample a. Define G'(s) def G(bar(s)), where bar(s) is the complement of s b. Define G'(s) def bar(G(s)) c. Define G'(s) def G(0^(|s|)||s) d. Define G'(s) def G(s) || G(s+1)