Concept:A rough surface increases the friction between the belt and the load.Explanation:Conveyor belts move loads from one place to another.If the surface is smooth, the load can slide backward or slip off.Making the surface rough increases the frictional force acting on the load.This stronger friction grips the load and holds it steady on the moving belt.So, the load moves along with the belt without slipping.Answer:B. prevent the loads from slipping