Well, Newtons first law of motion says that an object in motion stays in motion until an unbalanced force acts upon it, so, the correct answer would be B, it proves Newtons first law because friction is an unbalanced force.
"Friction is a force that opposes the motion of objects. Friction is always involved in everyday situations. It is what slows the motion of moving objects, so you don't see objects moving forever in a straight line."
