Sam and his Dad went grocery shopping. As they went up and down the aisle, adding items to their cart, something changed. The cart got heavier as they added groceries. As the cart became heavier, it also became harder to push. What else MOST LIKELY changed as Sam and his Dad shopped? A) The force of the cart. B) The speed of the cart. C) The size of the cart. D) The direction of the cart.