*Question E8B04:
What is the modulation index of an FM phone signal having a maximum carrier deviation of plus or minus 6 kHz if the highest modulating frequency is 2 kHz?*  

*Correct Answer is  B: 3*  

### AI Response: (may contain errors)  

To find the modulation index of an FM (Frequency Modulation) signal, we use the formula:

$$
\text{Modulation Index} (h) = \frac{\Delta f}{f_m}
$$

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

In this case:
- The maximum carrier deviation, $\Delta f$, is given as ±6 kHz, which is 6000 Hz.
- The highest modulating frequency, $f_m$, is given as 2 kHz, which is 2000 Hz.

Now, substituting the values into the formula:

$$
h = \frac{6000 \text{ Hz}}{2000 \text{ Hz}} = 3
$$

### Explanation of the Correct Answer:
- The modulation index is calculated to be 3, which means that the frequency deviation is three times the highest modulating frequency. This indicates a significant amount of modulation, which is typical for FM signals.

### Why the Other Choices are Incorrect:
- **Choice A: 0.3**
  - This would imply a very low modulation index, suggesting that the frequency deviation is much smaller than the modulating frequency, which is not the case here.
  
- **Choice C: 0.6**
  - Similar to choice A, this value suggests that the deviation is less than the modulating frequency, which does not match the given parameters.
  
- **Choice D: 6**
  - This would imply that the frequency deviation is six times the modulating frequency, which is incorrect based on the provided values.

### Summary:
- The correct modulation index for the given FM phone signal is 3, calculated using the formula for modulation index. The other choices do not accurately reflect the relationship between the frequency deviation and the modulating frequency.