Which of the following forces are third-law partners?

A. A thrust force from its propeller pulls a plane forward; a drag force pushes it backwards

B. A car exerts a forward force on a trailer; the trailer tugs backward on car.

C. A box is being pushed across the floor at constant velociy; the force of friction pushes backwards on the box.

D. Gravity pulls down on a person sitting in a chair; the chair pushes back up on the person.