A cart is rolling across the floor at a constant velocity of 2 m/s to the right. The cart is pushed again to the right, and it starts to accelerate. How are the force of the push and acceleration of the cart related?
A. The force and acceleration are not related.
B. The force of gravity makes the car accelerate.
C. The balanced push causes the cart to accelerate.
D. The unbalanced push causes the cart to accelerate.