Question

One body exert force on other body then how and why the other body apply same force and in opposite direction???

Answer 1

Let taken object A and object B
Object A cannot exert a force on Object B without Object Bexerting a force on A (equal in magnitude and opposite indirection): Newton's Third Law (N3): Whenever a body exerts aforce on another body, the latterexerts a force of equal magnitude and opposite direction on the former. ... All forces come in pairs.
Formally stated, Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object.