(b) it increases because when a spring is compressed it stores it energy in potential energy and then converts it into kinetic energy when released. it follows newtns third law of motion.

Explanation:

Compression of a Coil Spring:
When a coil spring is compressed, external force is applied on it to reduce its length. This force causes the coils to come closer together, resulting in compression of the spring.

Work Done:
Work is done when a force is applied on an object and it moves in the direction of the force. In the case of a compressed coil spring, work is done on the spring when it is compressed.

Elastic Potential Energy:
Elastic potential energy is the energy stored in an elastic object when it is deformed. In the case of a compressed coil spring, energy is stored in the spring due to its deformation.

Conservation of Energy:
According to the law of conservation of energy, energy cannot be created or destroyed, but it can be transferred or transformed from one form to another. In the case of a compressed coil spring, the work done on the spring is transformed into elastic potential energy.

Explanation of Option B:
The correct answer is option B - the elastic potential energy increases. When a coil spring is compressed, work is done on it to reduce its length. This work done on the spring is converted into elastic potential energy, resulting in an increase in the energy stored in the spring.

The compression of the coil spring increases the potential energy stored in it because the energy is being transferred from the external force applied to the spring into the spring itself, causing it to become more compressed. This increase in potential energy is due to the increased deformation of the spring, as the coils are forced closer together.

Therefore, when a coil spring is compressed, the elastic potential energy increases.