If a body does not change its direction during the course of its motion, then ……………..

Hint: We can modify the speed and therefore the direction of a moving body or a moving object by applying ice externally on the body or the object. By applying the first law of motion of Newton that can be understood.

Complete step-by-step solution:
The first law of motion of Newton states that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or moves in a straight line at a uniform speed otherwise it is acted upon by a force.
So if a body does not change its direction during its motion it's clearly shown that there is no external force acting on it. And, it is moving in a straight line or path with a uniform velocity. An object that's not moving won't begin moving unless a force is applied to that. In fact, even moving objects don't change their motion unless forces act on them. A force will change the motion of an associate degree object by dynamically the thing's speed or the direction the object is moving or each.
The Path length associated displacement becomes equal if an object doesn't modify its direction.

Note: When speed and direction of motion of a body don't modification the body,
That is once a body moves during a circular path, the direction of speed isn't identical at any 2 points. And once there's a modification within the direction of speed of the body, its rate isn't uniform. Hence, the circular motion is accelerated although the speed of the object is constant.