Circular motion refers to the motion of an object along a circular path. In circular motion, the direction of motion changes continuously, which is why the correct answer is option 'B'.

Explanation:

1. Direction of motion changes continuously:
In circular motion, an object moves along a curved path, constantly changing its direction. This is because the object is always changing its position with respect to the center of the circle. As the object moves around the circle, it continuously changes its orientation, resulting in a continuous change in the direction of motion.

2. Velocity is constant:
While the direction of motion changes continuously in circular motion, the magnitude of velocity remains constant. The velocity of an object in circular motion is defined as the rate of change of displacement with respect to time. Since the object is moving along a circular path, its displacement is constantly changing direction, but its magnitude remains constant. Therefore, the object's velocity in circular motion is constant, but its direction changes continuously.

3. Acceleration is zero:
In circular motion, the acceleration of an object is directed towards the center of the circle and is known as centripetal acceleration. The magnitude of centripetal acceleration is given by the formula a = v^2 / r, where v is the velocity of the object and r is the radius of the circle. However, despite the presence of acceleration, the net acceleration in circular motion is zero in the absence of any external forces. This is because the centripetal acceleration is always perpendicular to the velocity vector, resulting in a constant magnitude of velocity and no change in speed.

In summary:
In circular motion, the direction of motion changes continuously, while the velocity remains constant. The acceleration is zero in the absence of any external forces.