*Question G2C09:
What does the Q signal “QSL” mean?*  

*Correct Answer is  C: I have received and understood*  

### AI Response: (may contain errors)  

The Q signal "QSL" is used in amateur radio communication to convey specific information. 

1. **Correct Answer: "I have received and understood"**  
   - The Q signal "QSL" specifically means that the operator has received the message and understands it. This is a standard abbreviation used in radio communications to confirm receipt of information.

2. **Why the other choices are incorrect:**
   - **A: Send slower**  
     - This is not the meaning of "QSL." The Q signal for sending slower is "QRS."
   - **C: We have already confirmed the contact**  
     - While this may seem related, "QSL" does not imply that a previous contact has been confirmed; it simply indicates understanding of the current message.
   - **D: We have worked before**  
     - This is not correct either. The Q signal for indicating a previous contact is "QSO," which means a conversation or contact has taken place.

3. **Useful Rules of Thumb:**
   - Q signals are a set of standardized abbreviations used in radio communication to convey specific messages quickly and efficiently.
   - Familiarity with common Q signals can enhance communication and understanding in amateur radio operations.

In summary, "QSL" confirms receipt and understanding of a message, while the other options refer to different Q signals or concepts.