*Question E0A08:
What does SAR measure?*  

*Correct Answer is  C: The rate at which RF energy is absorbed by the body*  

### AI Response: (may contain errors)  

SAR, or Specific Absorption Rate, measures the rate at which radio frequency (RF) energy is absorbed by the human body. This is important for ensuring that exposure to RF energy remains within safe limits.

### Explanation:

1. **Correct Answer: C - The rate at which RF energy is absorbed by the body**
   - SAR is a measure used to quantify the amount of RF energy absorbed by the body when exposed to an RF electromagnetic field. It is expressed in watts per kilogram (W/kg). This measurement is crucial for assessing compliance with safety guidelines and regulations to protect human health.

2. **Why the other choices are incorrect:**
   - **A: Signal attenuation ratio**
     - This refers to the reduction in signal strength as it travels through a medium, not the absorption by the body.
   - **B: Signal amplification rating**
     - This describes how much a signal is increased in strength, typically by an amplifier, and is unrelated to body absorption.
   - **D: The rate of RF energy reflected from stationary terrain**
     - This pertains to how much RF energy bounces back from surfaces like the ground or buildings, not absorption by the body.

### Useful Information:

- **SAR Formula:**
  - While the exam does not require you to calculate SAR, it's useful to know that SAR is determined by the electric field strength, the conductivity of the tissue, and the density of the tissue.
  
- **Safety Guidelines:**
  - Regulatory bodies like the FCC set limits on SAR to ensure that devices like mobile phones are safe for use. These limits are based on scientific studies of RF exposure and its effects on human health.

Understanding SAR is essential for ensuring that RF devices are used safely and within regulatory limits.