Answer should be A.
We have to store frequencies. In the range [1,2, ... , 100] there are 50 numbers which are greater than 50. To store the frequency we can create an integer array, say freq, of 50 elements and then value of
freq[0] denotes the frequency of rank 51,
freq[1] denotes the frequency of rank 52, and so on and finally,
freq[49] denotes the frequency of rank 100
So at the minimum, we need array of 50 elements.