Newton's Third Law predicts that during a collision between two carts, when the sum of the forces acting on the system are zero:

The two carts will experience an impulse of the same magnitude, but of opposite directions.

Explanation:

Newton's third law proves that though action and reaction are the same, but they are opposite to each other.

i.e = -

where: and have equal value.

Impulse = F x t

where F is the force on the object and t is the time of impact.

In the given question, since the collision takes place in a given time.

Then;

x = - x

⇒ = -

Thus, since the sum of the forces acting on the system are zero, then the two carts experience an impulse of the same magnitude but opposite in directions.

it is b. absorbs thermal energy