A horizontal applied force of magnitude 25 N acts on a block sliding on a horizontal surface. The force of friction between the block and the surface has magnitude 8 N. If the direction of the applied force is reversed which of the following is true?
A. the magnitude of the velocity of the block will remain constant.
B. the magnitude of the acceleration of the block decreases
C. The magnitude of the net force on the block increases as compared to before.
D. the magnitude of the net force on the block will remain the same as before