The law of conversation of momentum explains that the momentum after a collision is?

is neither lost or gained

Step-by-step explanation:

The law of conversation tells us that energy can't be created or destroyed. So, the total energy of an isolated system should be constant.

This also works for momentum. When 2 objects collide, their total momentum will not change. Some of the energy can be transferred which change the momentum of individual object, but not the sum/total.