*Question E2C10:
Why do DX stations often transmit and receive on different frequencies?*  

*Correct Answer is  D: All these choices are correct*  

### AI Response: (may contain errors)  

To understand why DX stations often transmit and receive on different frequencies, let's analyze the correct answer and the other choices.

### Correct Answer: D - All these choices are correct

1. **Choice A: Prohibited Frequencies**
   - Some DX stations may operate on frequencies that are not allowed for certain responding stations. By using different frequencies for transmitting and receiving, they can avoid legal issues and ensure compliance with regulations.

2. **Choice B: Separation of Stations**
   - Using different frequencies helps to separate the calling stations from the DX station. This reduces congestion on the calling frequency and allows for clearer communication, as multiple stations can call in without interfering with each other.

3. **Choice C: Improve Operating Efficiency**
   - Transmitting and receiving on different frequencies can reduce interference. When stations operate on the same frequency, they can cause overlapping signals, leading to poor communication quality. By separating the frequencies, the DX station can manage incoming calls more effectively and maintain a clearer signal.

### Why the Other Choices Are Incorrect

- Since all the choices (A, B, and C) are valid reasons for using different frequencies, there are no incorrect choices in this context. Each choice contributes to the overall understanding of why DX stations adopt this practice.

### Summary

Using different frequencies for transmitting and receiving is a common practice in DX operations for several reasons:
- Compliance with regulations
- Reducing congestion and interference
- Improving overall communication efficiency

This practice is essential for effective communication in the crowded environment of amateur radio, especially during DX operations.