For every string s, let s be the string formed by taking the bitwise complement of the string s. For example 101 = 010 and 0010 = 1101. Suppose that G is a psuedorandom number generator (PRG) with expansion factor l. Which amongst the following functions are psuedorandom number generators? (Explain why?) (a) G_1 (s) = G (s) for every string s. (b) G_2 (s) = G (s) for every string s. (c) G_3 (s) = G (s) || G (s) for every string s where G (s) || G (s) means concatenation of the bitstrings G (s) and G (s). (d) G_4 (s) = res (G (s)) where res(G (s)) is the string obtained from the bitstring G (s) by removing the first and last digits of the bitstring G (s)