*Question T3C04:
Which of the following types of propagation is most commonly associated with occasional strong signals on the 10, 6, and 2 meter bands from beyond the radio horizon?*  

*Correct Answer is  B: Sporadic E*  

### AI Response: (may contain errors)  

The correct answer to the question is **B: Sporadic E**. Here's why:

### Explanation of the Correct Answer:
- **Sporadic E propagation** occurs when there are temporary layers of ionization in the E region of the ionosphere. This type of propagation is characterized by:
  - Occasional strong signals on the 10, 6, and 2 meter bands.
  - Signals can travel beyond the radio horizon due to the reflection of radio waves off these ionized layers.
  - It typically happens during the summer months and can lead to unexpected long-distance communication.

### Why the Other Choices are Incorrect:
- **A: Backscatter**
  - Backscatter refers to signals that are reflected back towards the transmitter from the ionosphere. This is more common at lower frequencies and does not typically result in strong signals from beyond the radio horizon on the specified bands.

- **C: D region absorption**
  - The D region of the ionosphere primarily absorbs radio waves, especially at lower frequencies. This absorption is not conducive to strong signal propagation, particularly on the higher frequency bands like 10, 6, and 2 meters.

- **D: Gray-line propagation**
  - Gray-line propagation occurs at dawn or dusk when the sun is just below the horizon. It can enhance signals over short distances but is not specifically associated with the strong signals from beyond the radio horizon on the specified bands.

### Summary:
- **Sporadic E** is the most relevant type of propagation for strong signals on the 10, 6, and 2 meter bands from beyond the radio horizon due to its unique ionospheric conditions.
- The other options either describe different propagation mechanisms or conditions that do not lead to the same effects on the specified bands. 

This understanding of propagation types is crucial for effective communication in amateur radio.