Answer:
c) Their momentum changes are the same size.
Step-by-step explanation:
In order to understand this you need to remember that the momentum is divided equally in the collision, so the correct answer to this is the fact that their momentum will changes the same, because that is how energy is preserved, the thing that could be different is that they are affected different by that momentum, it would probably affect differently the small car and the tractor, it would probably have a lot of impact for the small car.