Friction: • The friction force is resistance caused by two surfaces moving past each other. • It acts in a direction opposite to motion. • It depends on the nature of the surface. • The friction act parallels the contact surface. Film friction: • When we apply oil between two surfaces, • The surface does not become completely frictionless. • There is friction between two surfaces due to the formation, • of thin oil film between two surfaces. • The friction form is known as film friction. Conclusion: From the above statement, we conclude that, • When the two surfaces in contact have a very thin layer of lubricant film friction is developed between the two surfaces. The two surfaces in contact have a very thin layer of lubricant in between them, it is known as Flim friction. Please Note: As per the first answer key published by the commission, option (3) is given as the correct answer. But as per the final answer key, the question has been canceled by the commission.