If a heavy load is pulled along a smooth horizontal surface, then the force acting on the load may be: a. The applied force in the horizontal direction. b. The force of gravity acting on the load vertically downwards.c. The force of friction acting in the horizontal direction opposite the motion. d. Reaction force due to the horizontal surface. Which of the above statements are true?

• A. a and b
• B. a, b, c and d
• C. b, c and d
• D. a, b and c