Assertion : A body is moving along a circle with a constant speed. Its angular momentum about the centre of the circle remains constant
Reason : In this situation, a constant non-zero torque acts on the body.

Options

A. If both Assertion and Reason are correct 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 fasle
D. If Assertion is false but Reason is true

Explanation

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

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that a body moving in a circle with constant speed has a constant angular momentum about the center of the circle.
- For an object moving in a circular path, the angular momentum \( L \) can be expressed as:
\[ L = m \cdot v \cdot r_{\perpendicular} \]
- Here, \( m \) is the mass of the body, \( v \) is the constant speed, and \( r_{\perpendicular} \) is the perpendicular distance from the center of the circle to the line of action of the velocity vector.

2. **Analyzing Angular Momentum**:
- Since the speed \( v \), mass \( m \), and the radius \( r_{\perpendicular} \) (which remains constant as the body moves in a circle) are all constant, the angular momentum \( L \) remains constant.
- Therefore, the assertion is true.

3. **Understanding the Reason**:
- The reason states that there is a constant non-zero torque acting on the body.
- Torque (\( \tau \)) is related to the rate of change of angular momentum:
\[ \tau = \frac{dL}{dt} \]
- Since we established that the angular momentum \( L \) is constant, the rate of change of angular momentum \( \frac{dL}{dt} \) is zero.

4. **Conclusion about Torque**:
- If \( \frac{dL}{dt} = 0 \), then the torque \( \tau \) must also be zero.
- Therefore, the reason provided is false because it states that there is a constant non-zero torque acting on the body, which contradicts our finding that the torque is zero.

5. **Final Evaluation**:
- The assertion is true, but the reason is false. Hence, the correct conclusion is that the assertion is correct while the reason is incorrect.

### Final Answer:
- Assertion: True
- Reason: False