Assertion : In earthworm, setae show perichaetine arrangement.
Reason: Setae are present in a ring in middle of most of segments.

Options

A. If both Assertion and Reason are true and Reason is correct explanation of Assertion
B. If both Assertion and Reason are true but Reason is not a correct explanation of Assertion.
C. If Assertion is true but Reason is False
D. If both Assertion and Reason are false

Answer

To analyze the given assertion and reason about the arrangement of setae in earthworms, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that in earthworms, setae show a perichaetine arrangement.
- **Explanation**: Setae are small bristle-like structures that help earthworms in locomotion and anchoring. The term "perichaetine" refers to the arrangement of these setae around the body segments of the earthworm.

**Hint**: Recall what setae are and their function in earthworms.

2. **Understanding the Reason**:
- The reason states that setae are present in a ring in the middle of most segments.
- **Explanation**: This is true as the setae are arranged in a circular pattern around the body segments, which is characteristic of the perichaetine arrangement.

**Hint**: Visualize the body structure of an earthworm and where the setae are located.

3. **Evaluating the Relationship**:
- Both the assertion and the reason are true statements. The arrangement of setae (perichaetine) is indeed characterized by their presence in a ring around the segments.
- **Explanation**: The reason provides a correct explanation for the assertion since the arrangement of setae in a ring is what defines the perichaetine arrangement.

**Hint**: Consider how the arrangement of setae contributes to the earthworm's movement.

4. **Conclusion**:
- Since both the assertion and reason are true, and the reason correctly explains the assertion, the correct answer is that both statements are true and the reason is the correct explanation of the assertion.

**Hint**: Review the options given in the question to determine the correct choice.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion.