Question

When a person walks on a rough surface, the frictional force exerted by the surface on the person is opposite to the direction of his motion.

Answer 1

KEY CONCEPT: Friction force opposes the relative motion of the surface of contact.
When a person walks on a rough surface, the foot is the surface of contact. When he pushes the foot backward, the motion of surface of contact tends to be backwards. Therefore the frictional force will act forward (in the direction of motion of the person)