Assertion (A): All machines suffer a loss of efficiency due to the frictional force acting on any moving member of that machine. Reason (R): The frictional force can be reduced by providing a thin film of lubricant between any two mating parts.

• A. if A is true but R is false.
• B. if both A and R are true but R is not the correct explanation of A.
• C. if both A and R are true and R is the correct explanation of A.
• D. if A is false but R is true.