(C) Circular motion is a movement of an object along the circumference of a circle or rotation along a circular path. It can be uniform with constant angular rate of rotation and constant speed or non-uniform with a changing rate of rotation. Since, the object's velocity vector is constantly changing direction, the moving object is undergoing acceleration by a centripetal force in the direction of the centre of rotation without this acceleration, the object would move in a straight line, according to Newton's laws of motion. Hence, the acceleration of the car is a non-zero but not a constant.