This exercise is from Introduction to Modern Cryptography (2nd Edition) by Katz & Lindell

Let G be a pseudorandom generator that on security paramter n > 1, takes as input bitstrings of length n and has expansion factor ((n) > 2n. 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) = G(81, . . . ,Fr/21), where s-81, . . . , 8n. (b) Define G(sG(s). (c) Define G,(s) = G(rotate(s, i)), where rotate(s, 1) rotates the bits of s to the right by one position