Final answer:
When an object changes direction to return to its original position, the VT slope of its position-time graph becomes negative, reflecting a change in direction and negative velocity.
Step-by-step explanation:
When an object changes direction and heads towards its original position, the slope (VT slope) of its position versus time graph becomes negative. This is because the object has reversed direction, indicating a negative velocity relative to the positive direction established in the problem. Therefore, the correct answer is D. Slope becomes negative.
The slope corresponds to the velocity of the object in a position versus time graph. If the object is moving back towards the original position, it implies that the slope of the graph has changed from positive (if initially moving away from the origin) to negative. This negative slope indicates that the object is now moving in the opposite direction.