*Question E0A03:
Over what range of frequencies are the FCC human body RF exposure limits most restrictive?*  

*Correct Answer is  C: 30 - 300 MHz*  

### AI Response: (may contain errors)  

The correct answer is C: 30 - 300 MHz.

1. **Why the correct answer is correct:**
   - The frequency range of 30 to 300 MHz is where the human body absorbs RF energy most efficiently. This is due to the size of the human body being comparable to the wavelength of RF signals in this range, leading to higher absorption and potential for heating effects. Therefore, the FCC has set more restrictive exposure limits in this range to protect human health.

2. **Why the other choices are incorrect:**
   - **A: 300 kHz - 3 MHz**: At these lower frequencies, the wavelength is much longer than the size of the human body, resulting in less efficient absorption and lower potential for harmful effects.
   - **B: 3 - 30 MHz**: While absorption is possible, it is not as efficient as in the 30 - 300 MHz range. The body does not resonate as effectively with these frequencies.
   - **D: 300 - 3000 MHz**: Although this range includes frequencies used by many communication devices, the absorption is less efficient compared to the 30 - 300 MHz range. The body does not resonate as strongly with these higher frequencies.

3. **Useful rules of thumb:**
   - The human body is most susceptible to RF energy when the frequency is such that the wavelength is comparable to the size of the body or its parts. This typically occurs in the VHF (Very High Frequency) range, which is 30 - 300 MHz.
   - The FCC sets exposure limits based on Specific Absorption Rate (SAR), which measures the rate at which the body absorbs RF energy. The limits are more stringent in the 30 - 300 MHz range to minimize health risks.