Assertion : Magnets should be placed in keepers.
Reason : Keepers prevent self-demagnetisation of magnets.

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 assertion is false but reason 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**:
- The assertion states that "Magnets should be placed in keepers."
- This means that when storing magnets, it is advisable to use keepers to maintain their magnetic properties.

2. **Understanding the Reason**:
- The reason given is "Keepers prevent self-demagnetization of magnets."
- This implies that keepers help to prevent the magnets from losing their magnetism over time.

3. **Explaining the Function of Keepers**:
- Keepers are typically made of soft iron or other magnetic materials.
- When magnets are stored with keepers, the magnetic field lines can flow through the keepers, which helps in maintaining the magnetic strength of the magnets.

4. **Analyzing the Relationship**:
- The assertion is true because it is indeed a good practice to store magnets in keepers.
- The reason is also true because keepers do prevent self-demagnetization by providing a closed magnetic circuit.

5. **Conclusion**:
- Both the assertion and the reason are true.
- The reason correctly explains why the assertion is true, as keepers help maintain the integrity of the magnets.

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