*Question E3B08:
How does the maximum range of ground-wave propagation change when the signal frequency is increased?*  

*Correct Answer is  C: It decreases*  

### AI Response: (may contain errors)  

Ground-wave propagation is a mode of radio wave propagation that follows the contour of the Earth. It is most effective at lower frequencies, particularly in the medium frequency (MF) and low frequency (LF) bands.

### Explanation:

1. **Correct Answer: C: It decreases**

   - As the signal frequency increases, the maximum range of ground-wave propagation decreases. This is because higher frequency signals are absorbed more by the Earth's surface and the atmosphere, reducing their ability to travel long distances along the ground.

2. **Why the other choices are incorrect:**

   - **A: It stays the same**  
     This is incorrect because the range of ground-wave propagation is frequency-dependent. Higher frequencies result in shorter ground-wave ranges.

   - **B: It increases**  
     This is incorrect because, as mentioned, higher frequencies are absorbed more, leading to a decrease in range, not an increase.

   - **D: It peaks at roughly 8 MHz**  
     This is incorrect because ground-wave propagation does not peak at 8 MHz. In fact, ground-wave propagation is more effective at lower frequencies, typically below 3 MHz.

### Useful Rule of Thumb:

- Ground-wave propagation is most effective at lower frequencies, such as those used in the AM broadcast band (around 530 kHz to 1700 kHz). As frequency increases, the effectiveness and range of ground-wave propagation decrease.