Assertion: When a particle moves with constant velocity its average velocity, its insttantaneous velocity and its speed are all equal in magnitude.
Reason: If the average velocity of a particle moving on a straight line is zero in a time interval, then it is possible that the instantaneous velocity is never zero in the internal.

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 both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that when a particle moves with constant velocity, its average velocity, instantaneous velocity, and speed are all equal in magnitude.
- **Constant Velocity**: This means that both the speed (magnitude of velocity) and the direction of the particle's motion do not change.
- Since the velocity is constant, the average velocity over any time interval will equal the constant velocity.
- The instantaneous velocity, defined as the velocity at a specific moment, will also equal the constant velocity throughout the motion.
- The speed, being the magnitude of velocity, will also remain constant and equal to the constant velocity.
- Therefore, the assertion is **True**.

2. **Understanding the Reason**:
- The reason states that if the average velocity of a particle moving in a straight line is zero over a time interval, it is possible for the instantaneous velocity to never be zero during that interval.
- **Average Velocity**: It is defined as the total displacement divided by the total time taken. If a particle returns to its starting point, the displacement is zero, making the average velocity zero.
- However, during the motion, the particle may have non-zero velocities at various points, including the possibility of changing direction.
- For example, if a particle moves from point A to point C and back to A, the average velocity is zero, but it can have positive velocity while moving to C and negative velocity while returning to A.
- However, at the exact point of turning (point C), the instantaneous velocity is zero because the particle momentarily stops before changing direction.
- Thus, the statement that the instantaneous velocity can never be zero is **False**.

3. **Conclusion**:
- The assertion is **True**.
- The reason is **False**.
- Therefore, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
- The assertion is true, and the reason is false.