Assertion : Vernalisation is the promotion of flowering by a period of low temperature.
Reason : It prevents precocious reproductive development late in the growing season.

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

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Vernalization is the promotion of flowering by a period of low temperature."
- This means that certain plants require exposure to cold temperatures for a specific duration to trigger their flowering process.

2. **Understanding the Reason**:
- The reason states that "It prevents precocious reproductive development late in the growing season."
- This implies that vernalization helps to delay flowering until the plant has matured sufficiently, preventing it from flowering too early in the growing season.

3. **Evaluating the Truth of the Assertion**:
- The assertion is indeed true. Many plants, especially certain crops like wheat and barley, need a period of low temperature to flower properly.

4. **Evaluating the Truth of the Reason**:
- The reason is also true. Vernalization does help in preventing premature flowering, allowing the plant to mature adequately before it flowers.

5. **Determining the Relationship Between Assertion and Reason**:
- While both the assertion and reason are true, the reason does not directly explain the assertion. The assertion focuses on the requirement of low temperatures for flowering, while the reason discusses the prevention of premature flowering.

6. **Selecting the Correct Option**:
- Since both the assertion and reason are true, but the reason is not the correct explanation of the assertion, the correct option is: "Both assertion and reason are true, but reason is not the correct explanation of the assertion."

### Final Answer:
The correct option is: **Both assertion and reason are true, but reason is not the correct explanation of the assertion.**

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