Final answer:
The net forces exerted on the horse and cart are not the same, so they are not balanced forces.
Step-by-step explanation:
The statement that best describes the forces acting on the horse and buggy is that the net forces exerted on the horse and cart are not the same, so they are not balanced forces.
When the horse pulls the buggy, it exerts a force in one direction, while the buggy exerts an equal and opposite force on the horse. These forces are not balanced, resulting in a net force on the system. This net force causes the horse and the buggy to accelerate in the direction of the net force.