An object is said to be in motion its position (with respect to another object)
A. changes with time
B. does not change with time
C. does not change
D. is the same as before

Hint: The motion of an object can be defined by its velocity.
Use an example by taking two bodies at different motion and analyze their position with time.

Complete step by step solution:
We know that the state of motion is the condition of the motion of an object and it is defined by its velocity, that is the position of the object changes with respect to time. If the velocity of an object is zero, then the object is not moving, that is the object is at rest whereas the object has some velocity, then it is moving with a certain speed in a direction.
Let us understand with the help of an example, when you projected a stone in the air, it has some initial velocity and it changes its position with respect to you as it moves further and further as time proceeds.
Let us understand with another example, if two cars are moving in opposite directions, then the position of one car is constantly changing with respect to another car as time proceeds and vice- versa.
Thus, the object is said to be in motion and its position (with respect to another object) changes with time.

So, the correct answer is “Option A”.

Note:
Motion can be defined as the change in the position with respect to a reference point, which is basically a point or an object through which you measure your position after a certain period of time.
If the velocity of an object is zero, then the object is not moving.