Assertion (A): Decomposers are the scavengers in the ecosystem.
Reason (R): A food chain starts with decomposers.

Options

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

Explanation

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

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**: The assertion states that "Decomposers are the scavengers in the ecosystem."
- Decomposers, such as fungi and bacteria, break down dead organic matter and recycle nutrients back into the ecosystem.
- This role is similar to that of scavengers, which consume dead organisms. Therefore, the assertion is **true**.

2. **Understanding the Reason (R)**: The reason states that "A food chain starts with decomposers."
- In a typical food chain, the first level consists of producers (like plants) that convert sunlight into energy through photosynthesis.
- Decomposers come into play at the end of the food chain, breaking down dead organisms and returning nutrients to the soil. Hence, the reason is **false**.

3. **Evaluating the Options**:
- Option 1: Both are true, and the reason is the correct explanation of the assertion. (Incorrect)
- Option 2: Both are true, but the reason is not the correct explanation. (Incorrect)
- Option 3: Assertion is true, but the reason is false. (Correct)
- Option 4: Assertion is false, and the reason is true. (Incorrect)

4. **Conclusion**: The correct answer is Option 3: Assertion is true, but the reason is false.