How many flip-flops are required to divide a signal frequency by 16?

Answer: A. 4

Each flip-flop divides by 2, so chained flip-flops divide by 2 to the power of the count. 2 x 2 x 2 x 2 = 16, so 4 flip-flops are needed.

Tip: 2^4 = 16, so four flip-flops.