C)constant change in direction
because As an object moves in a circle, it is constantly changing its direction. At all instances, the object is moving tangent to the circle. Since the direction of the velocity vector is the same as the direction of the object's motion, the velocity vector is directed tangent to the circle as well.

Explanation:

When an object is moving in uniform circular motion, it means that it is moving along a circular path at a constant speed. Let's analyze the options given:

a) Constant acceleration: Acceleration is defined as the rate of change of velocity. In uniform circular motion, the speed of the object remains constant, but its direction continuously changes. Therefore, there is a change in velocity, and hence, the object is experiencing acceleration. Thus, option 'a' is incorrect.

b) Constant velocity: Velocity is a vector quantity that includes both speed and direction. In uniform circular motion, the object's direction is continuously changing, even though the speed remains constant. Therefore, the object does not have a constant velocity. Thus, option 'b' is incorrect.

c) Constant change in direction: In uniform circular motion, the object continuously changes its direction as it moves along the circular path. The change in direction is constant because the object is always turning towards the center of the circle. Therefore, option 'c' is correct.

d) Constant change in motion: This option is not a precise scientific term. Motion is a broad concept that includes various aspects such as speed, direction, and acceleration. In the context of uniform circular motion, the object's speed remains constant, but its direction changes. Therefore, it is not accurate to say that there is a constant change in motion. Thus, option 'd' is incorrect.

In conclusion, when an object is moving with uniform circular motion, it experiences a constant change in direction. This means that the object continuously turns towards the center of the circle while maintaining a constant speed.