Answer:
B. Newton's third law
Explanation:
When two bodies collide the moment remains constant.
This occurs because we define a system that is formed by the two bodies, so that the forces last = before the shock are forces of action and reaction, from one body to the other, so that for the system (two bodies) the force total is zero, we assume that the system is isolated from the outside.
In summary, the initial establishment is a consequence of Newton's third law
