A particle is moving along a straight line. The displacement of the particle becomes zero in a certain time `(tgt 0).` The perticle does not undergo any collision.

Options

A. The acceleration of the particle may be zero always
B. The acceleration of the particle may be zero uniform
C. The velocity of the particle must be zero at some instant
D. The acceleration of the particle must change its direction

Explanation

To solve the problem, we need to analyze the motion of the particle given that its displacement becomes zero after a certain time \( t \) (where \( t > 0 \)).

### Step-by-Step Solution:

1. **Understanding Displacement**:
- Displacement is defined as the change in position of an object. If the displacement is zero after a certain time, it means that the particle has returned to its original position.

2. **Analyzing Motion**:
- Since the particle returns to its starting point, it must have moved away from that point and then come back. This implies that at some point during its motion, the particle must have stopped momentarily before reversing direction.

3. **Velocity Consideration**:
- For the particle to return to its original position, its velocity must be zero at some instant. This is because, to change direction, an object must first come to a stop. Therefore, the velocity of the particle must be zero at some point during its motion.

4. **Acceleration Consideration**:
- The acceleration of the particle can vary. It is possible for the particle to have zero acceleration at some points (for example, if it moves with constant velocity), but it can also have non-zero acceleration when it is speeding up or slowing down. Thus, while the acceleration may be zero at certain times, it is not necessarily always zero.

5. **Direction of Acceleration**:
- The statement regarding the acceleration changing direction is not necessarily true. The acceleration can remain in the same direction or change direction depending on the motion of the particle. Therefore, it is incorrect to assert that the acceleration must change direction.

### Conclusion:
Based on the analysis:
- The velocity of the particle must be zero at some instant (Correct).
- The acceleration of the particle may be zero at some points but not always (Correct).
- The acceleration does not necessarily have to change direction (Incorrect).

Thus, the correct options are B and C.