Motion of an object is _______ if its velocity is constant.

uniform

The correct answer is option 4. uniform.

Motion of an object is Uniform.

If the velocity of an object is constant, meaning it does not change in magnitude or direction over time, the motion is considered uniform. In uniform motion, the object covers equal distances in equal intervals of time, and its velocity-time graph appears as a straight line. Therefore, when the velocity of an object is constant, its motion is uniform.