Assertion : Phytoplankton, algae & higher plants are chief producers in pond ecosystem.
Reason : Many algae are responsible for production of ethanol.

Options

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

Answer

To solve the assertion and reason question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Phytoplankton, algae & higher plants are chief producers in pond ecosystems."
- This is true because in a pond ecosystem, phytoplankton (microscopic plants), algae, and higher plants (like water lilies and cattails) are the primary producers. They perform photosynthesis, converting sunlight into energy and providing food for other organisms in the ecosystem.

2. **Understanding the Reason**:
- The reason states that "Many algae are responsible for the production of ethanol."
- This statement is also true. Certain species of algae can be used to produce ethanol through fermentation processes. Algae can contain polysaccharides that can be converted into sugars, which can then be fermented to produce ethanol.

3. **Evaluating the Relationship**:
- Now we need to determine if the reason is a correct explanation of the assertion. While both statements are true, the reason does not explain why phytoplankton, algae, and higher plants are considered chief producers in pond ecosystems. The assertion focuses on their role in the ecosystem, while the reason discusses a specific application (ethanol production) that is not directly related to their role as producers.

4. **Conclusion**:
- Therefore, the assertion is true, the reason is true, but the reason is not a correct explanation of the assertion.

### Final Answer:
- The correct option is **B**: Assertion is true, Reason is true, but Reason is not the correct explanation of Assertion.