Which force acts during projectile motion? A. Nuclear force B. Electric force C. Gravity D. Magnetic force

Option (C) is correct.

A projectile is an object launched at an angle with the horizontal and allowed to move freely under the effect of gravity alone.

Thus the only external force acting on a projectile is the force of gravity. There may be the force of air friction acting but for all practical purposes, we neglect its effect.

Thus only force of gravity acts during projectile motion.