A network designer asked you how many subnets (S) bits does he need to create 100 subnets?

(A) 4
(B) 5
(C) 7

7 bits are enough to create 100 subnets. You need to follow the formula of 2S > number of subnets to find out the required number of subnet bits to create 200 subnets.
*S = number of subnet bits

For example:
2^5 = 32 < 100 is not large enough
2^6 = 64 < 100 is not large enough
2^7 = 128 > 100 is enough