*Question E8B09:
What is deviation ratio?*  

*Correct Answer is  B: The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency*  

### AI Response: (may contain errors)  

The correct answer to the question about deviation ratio is:

**B: The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency.**

### Explanation of the Correct Answer:
- The deviation ratio is a key concept in frequency modulation (FM). It quantifies how much the carrier frequency deviates from its center frequency in relation to the highest frequency of the audio signal being used to modulate it.
- Mathematically, it can be expressed as:

$$
\text{Deviation Ratio} = \frac{\Delta f}{f_m}
$$

where:
- $\Delta f$ = maximum frequency deviation (in Hz)
- $f_m$ = highest audio modulating frequency (in Hz)

This ratio helps determine the bandwidth of the FM signal and is crucial for understanding how well the modulation will perform.

### Why the Other Choices are Incorrect:
- **A: The ratio of the audio modulating frequency to the center carrier frequency**
  - This choice incorrectly describes the relationship. The deviation ratio does not compare the modulating frequency to the carrier frequency; it focuses on the deviation and the modulating frequency.

- **C: The ratio of the carrier center frequency to the audio modulating frequency**
  - Similar to choice A, this option misrepresents the concept. The deviation ratio does not involve a direct comparison of the center frequency to the modulating frequency.

- **D: The ratio of the highest audio modulating frequency to the average audio modulating frequency**
  - This choice is not relevant to the deviation ratio. It discusses the relationship between different audio frequencies rather than the deviation of the carrier frequency.

### Summary:
- The deviation ratio is essential for understanding FM modulation and is defined as the maximum deviation of the carrier frequency divided by the highest frequency of the audio signal. This helps in determining the necessary bandwidth and ensuring effective transmission.