When can one say that work is done on the body

The correct option is: "When there is an increase in energy because of mechanical influence".

Understanding Work in Physics
In physics, work is defined as the transfer of energy that occurs when a force is applied to an object, causing it to displace. According to the work-energy theorem, the net work done on an object is directly equal to the change in its kinetic energy (or total mechanical energy if other forces are involved).

Why the Correct Option is Chosen:
When a mechanical influence (a force acting over a displacement) does work on a body, it transfers energy to that body. This process results in an increase in the energy of the body. Therefore, stating that work is done when there is an increase in energy because of mechanical influence is the most fundamental and accurate representation of the physical concept of work.

Why the Other Options are Incomplete or Incorrect:
1. "When the body experiences force": Simply experiencing a force is not sufficient. For example, if you push against a solid wall, you exert a force, but no work is done because the wall does not move. Thus, force alone does not guarantee work.
2. "When the body moves a certain distance": Motion alone is also not sufficient. If an object is moving at a constant velocity through space without any external force acting on it (inertial motion), no work is being done on it. Work requires both a force and a displacement in the direction of that force.