Assertion : In open water zone upto the depth to which light can penetrate , called photic zone .
Reason : The photic zone is categorised into euphotic and disphotic zone .

Options

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

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion**: The assertion states that the open water zone up to the depth to which light can penetrate is called the photic zone.
- The photic zone is indeed the layer of the ocean that receives sunlight, allowing for photosynthesis to occur.

2. **Understanding the Reason**: The reason provided states that the photic zone is categorized into euphotic and dysphotic zones.
- The photic zone is divided into two sub-zones:
- **Euphotic Zone**: This is the upper part of the photic zone where there is enough light for photosynthesis.
- **Dysphotic Zone**: This is the lower part of the photic zone where light is insufficient for photosynthesis.

3. **Evaluating the Truth of Both Statements**:
- Both the assertion and the reason are true. The assertion correctly defines the photic zone, and the reason accurately describes how the photic zone is further categorized.

4. **Determining the Relationship**:
- While both statements are true, the reason does not serve as a correct explanation for the assertion. The assertion describes what the photic zone is, while the reason provides additional information about its categorization but does not explain why it is called the photic zone.

5. **Conclusion**: Based on the evaluation, the correct answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

**Final Answer**: B - Both assertion and reason are true, but reason is not the correct explanation of the assertion.

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