different Boolean function with degree n =2^2^n here n =4 so total diff function will be 2^16 hence ans is D
if n=1 total Boolean function are 4 (e.g p,p',0,1)
if n=2 total Boolean function are 16 (e.g pq,pq',p'q,p'q',0,1,p+q,p+q',p'+q,p'+q',p,q,p',q', p xor q ,p xnor q)