Assertion : Crop rotation is the method in which crops are rotated to 90 degrees.
Reason : Crop rotation is used by the farmers so that they can sell different types of crops every year.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "Crop rotation is the method in which crops are rotated to 90 degrees." This is incorrect because crop rotation refers to the practice of growing different types of crops in the same area across a sequence of seasons, not rotating them physically at an angle.

2. **Understanding the Reason**: The reason given is "Crop rotation is used by the farmers so that they can sell different types of crops every year." This statement is partially true, as farmers do grow different crops, but the primary purpose of crop rotation is to maintain soil fertility and prevent nutrient depletion, rather than just for selling different crops.

3. **Analyzing the Relationship**: The assertion is incorrect, and while the reason has some truth, it does not accurately explain the primary purpose of crop rotation. The main goal of crop rotation is to manage soil nutrients and improve soil health.

4. **Conclusion**: Since the assertion is false and the reason is misleading regarding the primary purpose of crop rotation, we conclude that both statements are not correct in the context they are presented.

5. **Final Answer**: The correct option is that both the assertion and the reason are false.