Assertion: Septal nephridia take part in osmoregulation.
Reason: They are enteronephric.

Options

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

Answer

To analyze the assertion and reason provided in the question, let's break it down step by step.

### Step 1: Understand the Assertion
The assertion states that "Septal nephridia take part in osmoregulation."
- **Explanation**: Septal nephridia are specialized excretory structures found in earthworms. Their primary function is to regulate the internal water balance of the organism, which is a crucial aspect of osmoregulation.

### Step 2: Understand the Reason
The reason states that "They are enteronephric."
- **Explanation**: Enteronephric means that these nephridia open into the alimentary canal (the digestive tract). This anatomical feature allows septal nephridia to reabsorb water from the excretory fluid back into the body, thus playing a role in osmoregulation.

### Step 3: Evaluate the Truth of the Assertion and Reason
- **Assertion**: True. Septal nephridia do participate in osmoregulation by absorbing water from the excretory fluid.
- **Reason**: True. The enteronephric nature of septal nephridia allows them to connect with the alimentary canal, facilitating water reabsorption.

### Step 4: Determine if the Reason Explains the Assertion
Since the reason (being enteronephric) directly relates to how septal nephridia function in osmoregulation (by reabsorbing water), it serves as a correct explanation for the assertion.

### Conclusion
Both the assertion and the reason are true, and the reason provides a correct explanation for the assertion. Therefore, the answer is that both are true, and the reason is the correct explanation of the assertion.

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

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