The correct answer is (B):
A=36n-35n-1 = 36n-1n-35n
Since an - bn is divisible by a - b for all positive integral values of n, A is a multiple of 35 for any integral value of n and B is a set containing all the multiple of 35 including 0.
Hence, every member of A is in B but not every element of B is in A.