The best statement describing how jumping on a trampoline demonstrates Newton's third law is:
The trampoline pushes back with equal force but in the opposite direction.
This statement directly relates to Newton's third law, which states that for every action, there is an equal and opposite reaction. When a person jumps down, they exert a downward force on the trampoline, and the trampoline exerts an equal upward force on the person, propelling them upwards.