Assertion: A body,whatever its motion, is always at rest in a frame of reference which is fixed to the body itself.
Reason: The relative velocity of a body with respect to itself is zero.

Options

A. If both assertion `&` Reason are True `&` the Reason is a corrrect explanation of the Asserion.
B. If both Assertion `&` Reason are True but Reason is not correct explanation of the Assertion.
C. If Assertion is Trie but the Reason is False.
D. If both Assertion `&` Reason are false

Answer

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

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "A body, whatever its motion, is always at rest in a frame of reference which is fixed to the body itself."
- This means that if you consider a frame of reference that moves along with the body, the body will appear to be at rest in that frame.

2. **Understanding the Reason**:
- The reason states that "The relative velocity of a body with respect to itself is zero."
- This implies that if you measure the velocity of the body from a frame that is also moving with the body, there is no relative motion; hence, the velocity is zero.

3. **Analyzing the Relationship**:
- If we denote the velocity of the body as \( v_o \) and the velocity of the observer (or frame of reference) as \( v_1 \), then the relative velocity of the body with respect to the observer is given by:
\[ v_{relative} = v_o - v_1 \]
- When the observer is moving with the same velocity as the body (i.e., \( v_1 = v_o \)), the relative velocity becomes:
\[ v_{relative} = v_o - v_o = 0 \]
- This confirms that the body is at rest in its own frame of reference.

4. **Conclusion**:
- Both the assertion and the reason are true. The assertion correctly describes a fundamental principle of motion, and the reason provides a valid explanation for that principle.

### Final Answer:
- The assertion is true, and the reason is also true, with the reason being a correct explanation of the assertion.

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