Sam is pushing a cart. How can he make the cart move faster?

Responses
A He can add weight to the cart.He can add weight to the cart.
B He can push the cart up a ramp.He can push the cart up a ramp.
C He can take the wheels off the cart.He can take the wheels off the cart.
D He can increase the force of his push.

D He can increase the force of his push.