Assertion : Humus serves as a reservior of nutrients .
Reason: Humus is colloidal in nature.

Options

A. If both assertion and reason are true and the reason is a correct explanation of the assertion.
B. If both assertion and reason are true but reason is not a correct explanation of the 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 "Humus serves as a reservoir of nutrients."
- **Explanation**: Humus is a dark organic material in soil that is formed from the decomposition of plant and animal matter. It is rich in nutrients and plays a crucial role in soil fertility by holding nutrients that plants need for growth.

2. **Evaluating the Reason**: The reason given is that "Humus is colloidal in nature."
- **Explanation**: Colloids are mixtures where very small particles are dispersed throughout a substance. In the case of humus, it is indeed colloidal, meaning it consists of tiny particles that can hold water and nutrients effectively.

3. **Determining the Truth of the Statements**:
- Both the assertion and the reason are true. Humus does serve as a reservoir of nutrients, and it is colloidal in nature.

4. **Linking the Reason to the Assertion**:
- The reason provided (humus being colloidal) explains why humus can serve as a reservoir of nutrients. The colloidal nature allows humus to retain water and nutrients, making them available to plants.

5. **Conclusion**: Since both the assertion and reason are true, and the reason correctly explains the assertion, the answer is that both statements are true, and the reason is the correct explanation for the assertion.

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

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