It moves at a constant speed.
It moves in the same direction.
Explanation:
As stated by Newton's first law:
"an object in motion which has no external force acting on it will continue its motion at constant speed or it will stay at rest if it was at rest".
This is also related to Newton's second law, which states that the acceleration of an object is proportional to the net force applied to it: therefore, no external force means no acceleration, so no change in the motion of the object.
Therefore, only these two options:
It moves at a constant speed.
It moves in the same direction.
describes objects in motion that have no external force acting on it. On the contrary, all the other options involve a change in the velocity (either speed of direction) of the object, so they describe objects which are accelerating.
