Assertion: The work done against force of friction in the case of a disc rolling without slipping down an inclined plane is zero.
Reason: When the disc rolls without slipping, friction is required because for rolling condition velocity of point of contact is zero.
Options:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.