When the velocity of a body is variable, then :Its speed may be constantIts acceleration may be constantIts average acceleration may be constantAll of the above

The statement "When the velocity of a body is variable" can have different implications:

1. Its speed may be constant: This is generally not true. If the velocity (which is a vector quantity that includes both speed and direction) is changing, it usually means either the speed, the direction, or both are changing. However, there could be a special case where the body is moving in a circular path at a constant speed - the speed is constant, but the velocity is variable because the direction of motion is constantly changing.

2. Its acceleration may be constant: This can be true. If a body is moving with a variable velocity under a constant acceleration, it means the rate of change of its velocity is constant. This is the case for any object in free fall near the surface of the earth, where acceleration due to gravity is considered constant.

3. Its average acceleration may be constant: This is also possible. Average acceleration is the change in velocity divided by the change in time. Even if the velocity is variable, the average acceleration could be constant over a given time period.

4. All of the above: Given the explanations above, this option is not entirely correct. While the acceleration may be constant and the average acceleration may be constant, the speed of the body is not typically constant when the velocity is variable. However, as mentioned, there could be special cases where the speed is constant but the direction changes, causing variable velocity.

So, the answer depends on the specific conditions of the motion of the body.