*Question T2A12:
What should you do before calling CQ?*  

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

### AI Response: (may contain errors)  

Before calling CQ, it's important to ensure that the frequency is clear and that you are authorized to use it. Let's break down the correct answer and the reasoning behind each choice.

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

1. **Listen first to be sure that no one else is using the frequency (Choice A)**:
   - This is crucial because amateur radio operates on a shared basis. Listening helps you avoid interfering with ongoing communications. If you hear someone else, you should wait until they finish before calling CQ.

2. **Ask if the frequency is in use (Choice B)**:
   - If you are unsure after listening, it's polite to ask if the frequency is in use. This can be done by saying something like, "Is this frequency in use?" This shows good operating practice and courtesy to other operators.

3. **Make sure you are authorized to use that frequency (Choice C)**:
   - Each amateur radio operator has a specific license class that dictates which frequencies they are allowed to use. Before calling CQ, ensure that you are operating within your authorized bands and modes.

### Why the Other Choices Are Incorrect

- **Choice A**: While this choice is correct, it is only one part of the overall responsibility before calling CQ.
- **Choice B**: This choice is also correct but does not encompass the full range of necessary actions.
- **Choice C**: This choice is valid but does not address the need to check for other users on the frequency.

### Summary

All three actions are essential for responsible amateur radio operation. Therefore, the correct answer is D, as it encompasses all necessary precautions before calling CQ. 

### Rules of Thumb

- Always listen for a few moments before transmitting.
- If in doubt, ask if the frequency is in use.
- Know your license privileges and operate within them. 

By following these guidelines, you contribute to a respectful and efficient amateur radio environment.