Explanation: In digital frequency dividers, each flip-flop effectively divides the input frequency by a factor of 2. This is because a flip-flop, typically configured as a T-type or JK-type, changes its state on every second clock pulse, halving the frequency of the signal passing through it. To achieve a total frequency division by 4, you need to cascade multiple flip-flops. * One flip-flop divides the frequency by 2. * Two flip-flops, connected in series, will perform a division by $2 \times 2 = 4$. The output of the first flip-flop (divided by 2) feeds into the second flip-flop, which then divides it by another factor of 2. Therefore, two flip-flops are required to divide a signal frequency by 4. Options A, B, and C are incorrect as they would result in divisions by 2, 16, and 256 respectively.