Assertion: Mosses are of great ecological importance.
Reason: Mosses prevent soil erosion by forming dense mat on the soil

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

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "Mosses are of great ecological importance." This implies that mosses play a significant role in the ecosystem.

**Hint**: Consider what roles mosses might play in an ecosystem beyond just soil erosion.

2. **Understanding the Reason**: The reason provided is that "Mosses prevent soil erosion by forming a dense mat on the soil." This suggests that one of the functions of mosses is to protect the soil from being washed away.

**Hint**: Think about how mosses interact with the environment and how they might contribute to soil stability.

3. **Evaluating the Truth of the Assertion**: Mosses do indeed have great ecological importance. They are among the first organisms to colonize bare surfaces, contributing to soil formation and providing habitats for other organisms.

**Hint**: Reflect on the role of pioneer species in ecological succession.

4. **Evaluating the Truth of the Reason**: The reason is also true; mosses do help prevent soil erosion by forming a dense mat that protects the soil from rain and wind. However, this is just one aspect of their ecological role.

**Hint**: Consider other ecological functions that mosses might serve beyond preventing soil erosion.

5. **Determining the Relationship**: While both the assertion and reason are true, the reason does not fully explain why mosses are ecologically important. Their importance extends beyond just preventing soil erosion; they also contribute to soil formation and nutrient cycling.

**Hint**: Think about the broader implications of mosses in ecological processes.

6. **Conclusion**: Therefore, 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**: Both the assertion and reason are true, but the reason is not the correct explanation of the assertion.