What does the law of conservation of momentum say?

The law of conservation of momentum states that
the total momentum of a closed system does not change.

This means that when two objects collide
the total momentum of the objects before the collision
is the same as
the total momentum of the objects after the collision.

Julia would be observing a. static electricity was caused by her sweater rubbing against her shirt and transferring electrons. she didn't touch anything metal, so that would cancel out b.she most likely didn't rub her sweater against her hair either, so that cancels out c.she also didn't scoot across the carpet while trying to take her sweater off, that cancels out d.so that leaves a.a. is correct.