When a conservative force does positive work on a body
A. The potential energy increases
B. The potential energy decreases
C. Total energy increases
D. Total energy decreases

Hint: When a body is displaced in the direction of the force then it is known as positive work on a body. This causes the movement of objects in a direction either toward the center of force or away from the center of force. Due to this the separation between the body and center of force increases or decreases. This causes variation in the potential energy and kinetic energy of the body. Thus, keep the total energy constant. Use these basics to answer this question.

Complete step by step answer:
When the conservative force pushes or displaces the body in the direction of the force, the conservative force does a positive work on the body. Thus, the body moves towards the center of force. This causes a decrease in the separation between the body and the center of force. Thereby, decreasing the potential energy of the body and increasing the kinetic energy of the body.
Hence, when a conservative force does positive work on a body, the potential energy decreases.

So, the correct answer is option B i.e. the potential energy decreases.

Note:
When the conservative force pushes the body in the opposite direction of the force, the conservative force does a negative work on the body. This causes the body to move away from the center of force. Thus, the separation between the body and the center of force increases. Hence, when a conservative force does a negative work on the body, the potential of the body increases. As the potential energy increases, kinetic energy decreases.