Assertion: Brown algae vary from olive green to brown in colour.
Reason: Fucoxanthin is responsible for color variation in brown algae

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 analyze the assertion and reason provided in the question, we can break it down step by step:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Brown algae vary from olive green to brown in color."
- This means that brown algae can exhibit a range of colors, specifically from olive green to brown.

2. **Understanding the Reason**:
- The reason states that "Fucoxanthin is responsible for color variation in brown algae."
- Fucoxanthin is a pigment found in brown algae that contributes to their coloration.

3. **Connecting the Assertion and Reason**:
- To determine if the reason correctly explains the assertion, we need to establish if fucoxanthin is indeed responsible for the color variation described in the assertion.
- It is known that fucoxanthin is a major pigment in brown algae and is responsible for their characteristic brown color, as well as the variations in shades from olive green to brown.

4. **Conclusion**:
- Both the assertion and reason are true.
- The reason (fucoxanthin being responsible for color variation) correctly explains the assertion (the color variation of brown algae).

5. **Final Answer**:
- Therefore, both the assertion and reason are true, and the reason is the correct explanation for the assertion.