Final answer:
The correct answer is option C: its position is negative.
Step-by-step explanation:
The correct answer to the question is option C: its position is negative.
In the given information, it is stated that the particle moves along the x-axis and its position reaches 25 m, where it then reverses direction and begins to accelerate in the negative x direction.
This means that the position of the particle is changing from positive to negative, indicating that its position is negative.