*Question E7A03:
Which of the following can divide the frequency of a pulse train by 2?*  

*Correct Answer is  B: A flip-flop*  

### AI Response: (may contain errors)  

To understand which component can divide the frequency of a pulse train by 2, let's analyze each option:

### Correct Answer: B: A flip-flop

- **Explanation**: A flip-flop is a bistable device that can store one bit of data. When a pulse train is applied to the clock input of a flip-flop, it toggles its output state on every clock pulse. This means that for every two input pulses, the output changes state once, effectively dividing the frequency of the input signal by 2. 

### Why the Other Choices are Incorrect:

- **A: An XOR gate**: 
  - An XOR gate outputs a high signal only when the number of high inputs is odd. It does not inherently divide the frequency of a pulse train. Instead, it performs a logical operation and does not have the capability to toggle states in a manner that divides frequency.

- **C: An OR gate**: 
  - An OR gate outputs a high signal if at least one of its inputs is high. Like the XOR gate, it does not perform any frequency division. It simply combines signals without toggling states based on clock pulses.

- **D: A multiplexer**: 
  - A multiplexer selects one of several input signals and forwards the selected input into a single line. While it can manage multiple signals, it does not divide the frequency of a pulse train. Its function is more about routing signals rather than altering their frequency.

### Summary

- A flip-flop is the only component listed that can divide the frequency of a pulse train by 2 by toggling its output state with each clock pulse. The other components perform logical operations or signal routing but do not achieve frequency division. 

This understanding is crucial for the Extra Class exam, as it highlights the fundamental behavior of digital logic components.