*Question G8B13:
Which of the following is an odd-order intermodulation product of frequencies F1 and F2?*  

*Correct Answer is  C: 2F1-F2*  

### AI Response: (may contain errors)  

To determine which of the given options is an odd-order intermodulation product of frequencies $F1$ and $F2$, we need to understand what odd-order intermodulation products are.

### Odd-Order Intermodulation Products

- **Intermodulation products** are signals generated by the mixing of two or more frequencies in a non-linear device.
- **Odd-order products** are those where the sum of the coefficients (the numbers multiplying $F1$ and $F2$) is an odd number.

### Explanation of Choices

1. **Choice A: $5F1 - 3F2$**
   - The sum of the coefficients is $5 + (-3) = 2$, which is an even number.
   - Therefore, this is not an odd-order intermodulation product.

2. **Choice B: $3F1 - F2$**
   - The sum of the coefficients is $3 + (-1) = 2$, which is an even number.
   - Therefore, this is not an odd-order intermodulation product.

3. **Choice C: $2F1 - F2$**
   - The sum of the coefficients is $2 + (-1) = 1$, which is an odd number.
   - Therefore, this is an odd-order intermodulation product.

4. **Choice D: All these choices are correct**
   - This choice is incorrect because not all the given options are odd-order intermodulation products.

### Conclusion

The correct answer is **C: $2F1 - F2$** because it is the only option where the sum of the coefficients is an odd number, making it an odd-order intermodulation product.