Circular motion involves the motion of an object in a circular path. The object moves around the center of the circle with a constant speed. In circular motion, the object experiences various types of acceleration and velocity. Let’s discuss the given options to understand circular motion in detail.

Radial acceleration is non-zero:
Radial acceleration is the acceleration of an object towards the center of the circle. In circular motion, the direction of velocity changes continuously, and hence the object experiences a change in direction. This change in direction leads to the acceleration of the object towards the center of the circle, known as radial acceleration. Therefore, option ‘a’ is correct.

Radial velocity is zero:
Radial velocity is the velocity of an object in the radial direction, i.e., towards the center of the circle. In circular motion, the object moves in a circular path without any radial motion, i.e., the object moves perpendicular to the radius of the circle. Hence, radial velocity is zero in circular motion. Therefore, option ‘b’ is incorrect.

Body is in equilibrium:
Equilibrium is a state where the object is at rest or moves with a constant velocity. In circular motion, the object moves with a constant speed, but the direction of the velocity changes continuously. Therefore, the object is not at rest, but it is also not moving with a constant velocity. Hence, the body is not in equilibrium in circular motion. Therefore, option ‘c’ is incorrect.

All of the above:
From the above discussion, we can conclude that radial acceleration is non-zero, radial velocity is zero, and the body is not in equilibrium in circular motion. Therefore, option ‘d’ is the correct answer.

Conclusion:
Circular motion involves the motion of an object in a circular path. The object experiences various types of acceleration and velocity in circular motion. In circular motion, radial acceleration is non-zero, radial velocity is zero, and the body is not in equilibrium.