[A]: Endosperm is tripolid in angiosperms.
[R]: In gymnosperms, it is haploid.

Options

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

Answer

To solve the question regarding the assertion and reasoning about endosperm in angiosperms and gymnosperms, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "Endosperm is triploid in angiosperms."
- This is true because in angiosperms, the endosperm is formed from the fusion of one sperm cell with two polar nuclei, resulting in a triploid (3n) structure.

2. **Understanding the Reason (R)**:
- The reason states that "In gymnosperms, it is haploid."
- This is also true. In gymnosperms, the endosperm is formed before fertilization and is derived from the haploid megasporangium, making it haploid (n).

3. **Evaluating the Relationship**:
- The assertion and the reason are both true, but we need to determine if the reason correctly explains the assertion.
- The reason does not explain why the endosperm in angiosperms is triploid; it merely states a fact about gymnosperms.

4. **Conclusion**:
- Since both the assertion and reason are true, but the reason does not correctly explain the assertion, the correct answer is that both statements are true, but the reason is not the correct explanation for the assertion.

### Final Answer:
Both assertion and reason are true, but the reason is not the correct explanation for the assertion.