If k is the greatest positive integer such that 4^k is a divisor of 16! then k =  Pick:
A) 3
B) 4
C) 5
D) 6
E) 7

Rationale: "16 / 4 = 4 16 / 16 = 1 4 + 1 = 5 k = 5 answer : c"
Answer: C