Answer: (b) E/32, F/64. 

Solution:-
A + 1 = B  & 2 x 2 = 4,
B + 1 = C  & 4 x 2 = 8,
C + 1 = D & 8 x 2 = 16,

Same as,
D + 1 = E   &  16 x 2 = 32.
E + 1 = F &  32 x 2 = 64.

Hence, the correct answer is option (b) E/32, F/64.