*Question G3C11:
Which ionospheric region is the most absorbent of signals below 10 MHz during daylight hours?*  

*Correct Answer is  D: The D region*  

### AI Response: (may contain errors)  

The correct answer to the question is **D: The D region**. Here's why:

1. **Why the D region is correct:**
   - The D region of the ionosphere is located approximately 30 to 60 miles above the Earth's surface. During daylight hours, this region is highly ionized due to solar radiation, which leads to significant absorption of radio waves, especially those below 10 MHz. This absorption occurs because the D region contains a high concentration of free electrons, which scatter and absorb lower frequency signals.

2. **Why the other choices are incorrect:**
   - **A: The F2 region**: This region is the highest layer of the ionosphere and is primarily responsible for long-distance communication at higher frequencies (above 10 MHz). It does not absorb signals below 10 MHz significantly.
   - **B: The F1 region**: This region is also above the D region and is less significant in terms of absorption. It mainly contributes to the propagation of signals at higher frequencies, similar to the F2 region.
   - **C: The E region**: While the E region can cause some absorption, it is not as absorbent as the D region during daylight hours. The E region is more effective for frequencies around 10 MHz and above, but it does not have the same level of absorption for lower frequencies.

3. **Useful rules of thumb:**
   - The D region is most absorbent during the day due to increased ionization from solar radiation.
   - Frequencies below 10 MHz are generally more affected by the D region's absorption, especially during daylight.

In summary, the D region is the most absorbent of signals below 10 MHz during daylight hours, making it the correct answer for this question.