*Question G2C03:
What does it mean when a CW operator sends “KN” at the end of a transmission?*  

*Correct Answer is  C: Listening only for a specific station or stations*  

### AI Response: (may contain errors)  

When a CW (Morse code) operator sends "KN" at the end of a transmission, it indicates that they are listening only for a specific station or stations to respond. This is a common practice in CW operations to manage who should reply next.

### Explanation:

1. **Correct Answer: C: Listening only for a specific station or stations**
   - "KN" is a procedural signal in Morse code that means the operator is inviting only a specific station or stations to respond. It is used to control the flow of communication and ensure that only the intended recipient replies.

2. **Why the Other Choices are Incorrect:**
   - **A: No US stations should call**
     - This is incorrect because "KN" does not restrict calls based on geographic location. It is about specifying which station should respond, not about excluding stations from a particular country.
   - **B: Operating full break-in**
     - Full break-in, also known as "QSK," allows operators to hear incoming signals between their own transmissions. "KN" does not relate to this operating mode.
   - **D: Closing station now**
     - "KN" does not indicate that the station is closing or ending operations. Instead, it specifies that the operator is waiting for a particular station to reply.

### Useful Rule of Thumb:
- **"K" vs. "KN":**
  - "K" means "any station can respond," while "KN" specifies that only a particular station or stations should respond. This distinction helps manage who should reply in a CW conversation.