*Question E3B01:
Where is transequatorial propagation (TEP) most likely to occur?*  

*Correct Answer is  A: Between points separated by 2,000 miles to 3,000 miles over a path perpendicular to the geomagnetic equator*  

### AI Response: (may contain errors)  

Transequatorial propagation (TEP) is a radio wave propagation mode that occurs between locations on opposite sides of the geomagnetic equator. It is most effective over distances of approximately 2,000 to 3,000 miles (3,200 to 4,800 kilometers) and is typically perpendicular to the geomagnetic equator.

### Explanation:

1. **Correct Answer (A):**  
   - **Why it's correct:** TEP is most likely to occur between points separated by 2,000 to 3,000 miles over a path that is perpendicular to the geomagnetic equator. This is because the ionospheric conditions that facilitate TEP are strongest in this range and orientation, allowing signals to be refracted back to Earth effectively.

2. **Incorrect Choices:**
   - **Choice B:**  
     - **Why it's incorrect:** TEP does not typically occur between points located 1,500 to 2,000 miles apart on the geomagnetic equator. The distance is too short for TEP, which requires a longer path to utilize the ionospheric conditions effectively.
   - **Choice C:**  
     - **Why it's incorrect:** Antipodal points are located on opposite sides of the Earth, which is far beyond the range of TEP. TEP is not capable of supporting such long-distance communication.
   - **Choice D:**  
     - **Why it's incorrect:** The terminator is the line separating day from night on Earth. While it can affect propagation, TEP is specifically related to the geomagnetic equator, not the geographic equator or the terminator line.

### Useful Rule of Thumb:

- **TEP Path Length:**  
  TEP is effective for paths approximately 2,000 to 3,000 miles long, which is a key factor in identifying suitable conditions for this propagation mode.