Assertion: Communities that comprise of more species tend to be more stable.
Reason: A higher number of species results in less annual variation in total biomass.

Options

A. Assertion is correct, reason is correct, reason is a correct explanation for assertion.
B. Assertion is correct, reason is correct, reason is not a correct explanation for assertion
C. Assertion is correct, reason is incorrect
D. Assertion is incorrect, reason is correct.

Explanation

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

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that communities with more species tend to be more stable.
- Stability in ecological terms means that the community can maintain its structure and function despite disturbances.

**Hint**: Think about how diversity in species might contribute to the resilience of an ecosystem.

2. **Understanding the Reason**:
- The reason given is that a higher number of species results in less annual variation in total biomass.
- Total biomass refers to the total mass of living matter in a given area, and less variation means that the biomass remains relatively constant over the years.

**Hint**: Consider how different species might interact and contribute to the overall productivity of the ecosystem.

3. **Connecting Assertion and Reason**:
- A diverse community can buffer against fluctuations in environmental conditions, leading to more consistent biomass levels.
- More species can lead to more complex interactions (food webs), which can stabilize the ecosystem against disturbances.

**Hint**: Reflect on how species diversity might influence food chains and ecological interactions.

4. **Evaluating the Correctness**:
- Both the assertion and the reason are correct.
- The reason explains why the assertion is true: more species lead to less annual variation in biomass, contributing to community stability.

**Hint**: Look for relationships between the concepts of biodiversity, stability, and biomass variation.

5. **Conclusion**:
- Since both the assertion and the reason are correct and the reason provides a valid explanation for the assertion, we conclude that the correct answer is that both A and R are correct, and R is the correct explanation of A.

**Hint**: Always check if the reason logically supports the assertion in questions involving cause and effect.

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