______ is the external agency applied on a body to change its state of rest or uniform motion.

Force

The correct answer is option 4. Force.

The external agency applied on a body to change its state of rest or uniform motion is force.

Force is defined as any interaction that, when unopposed, will change the motion of an object. It can cause an object to accelerate, decelerate, stop, or change direction. In the context provided, force is the correct term to describe the external agency applied to change the state of motion of a body.