*Question E7A04:
How many flip-flops are required to divide a signal frequency by 16?*  

*Correct Answer is  A: 4*  

### AI Response: (may contain errors)  

To determine how many flip-flops are required to divide a signal frequency by 16, we can use the following rule:

- Each flip-flop divides the input frequency by 2.

To find the number of flip-flops ($N$) needed to achieve a division factor of $D$, we can use the formula:

$$D = 2^N$$

In this case, we want to divide the frequency by 16, so we set $D = 16$:

$$16 = 2^N$$

Now, we can solve for $N$:

- Since $16$ can be expressed as $2^4$, we have:

$$2^4 = 2^N$$

This implies that:

$$N = 4$$

### Explanation of the Correct Answer:
- **Correct Answer: 4**  
  You need 4 flip-flops to divide the frequency by 16 because each flip-flop divides the frequency by 2, and $2^4 = 16$.

### Explanation of Incorrect Choices:
- **Choice A: 4**  
  This is the correct answer, as explained above.

- **Choice B: 6**  
  If you had 6 flip-flops, the division would be $2^6 = 64$, which is too much for a division by 16.

- **Choice C: 8**  
  With 8 flip-flops, the division would be $2^8 = 256$, which is also too high.

- **Choice D: 16**  
  Using 16 flip-flops would result in a division of $2^{16} = 65,536$, far exceeding the requirement of dividing by 16.

### Summary:
- You need **4 flip-flops** to achieve a frequency division of 16, as each flip-flop halves the frequency, leading to the equation $D = 2^N$.