Internal forces do not affect the conservation of momentum because (a) they cancel each other, (b) their effects are canceled by external forces, (c) they can never produce a change in velocity, (d) newton's second law is not applicable to them.

Option A. Internal forces do not affect the conservation of the moment because they cancel each other. A system of particles subjected to external forces and also interact with each other, meet the internal forces Newton's third law and those internal forces are canceled and the moment is preserved.