What does newtons third law say about why momentum is conserved in collisions?

Newton's third law of motion is naturally applied to collisions between two objects. In a collision between two objects, both objects experience forces that are equal in magnitude and opposite in direction.For such a collision, the forces acting between the two objects are equal in magnitude and opposite in direction

The correct answer is:   [c]:     "it is the minimum amount of material needed to sustain a fission  reaction."