*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 $F_1$ and $F_2$, we need to understand how intermodulation products are generated.

### Odd-Order Intermodulation Products
Odd-order intermodulation products are generated by combining two frequencies in a non-linear mixer. The general formula for odd-order products can be expressed as:

$$
nF_1 \pm mF_2
$$

where $n$ and $m$ are odd integers (1, 3, 5, ...).

### Analyzing the Choices
Let's evaluate each option:

- **Choice A: $5F_1 - 3F_2$**
  - Here, $n = 5$ (odd) and $m = 3$ (odd).
  - This is an odd-order intermodulation product.

- **Choice B: $3F_1 - F_2$**
  - Here, $n = 3$ (odd) and $m = 1$ (odd).
  - This is also an odd-order intermodulation product.

- **Choice C: $2F_1 - F_2$**
  - Here, $n = 2$ (even) and $m = 1$ (odd).
  - This is NOT an odd-order intermodulation product because $n$ is even.

- **Choice D: All these choices are correct**
  - This is incorrect because not all choices are odd-order products.

### Conclusion
- The correct answer is **Choice C: $2F_1 - F_2$**, as it is the only option that does not fit the criteria for odd-order intermodulation products.
- Choices A and B are both valid odd-order products, while Choice D is incorrect because it claims all options are correct.

### Summary
- Odd-order intermodulation products must have both $n$ and $m$ as odd integers.
- The only choice that does not meet this criterion is $2F_1 - F_2$.