Consider the following statements: A. It is easier to walk on a smooth surface. B. A ball will roll down easily over a rough inclined plane compared to a smooth one. C. Frictional force opposes relative motion. D. Frictional force depends upon the nature of the surfaces in contact. Which of the above statements are correct?

Assertion (A): The coefficient of static friction is always less than the coefficient of kinetic friction. Reason (R): More force is required to start the motion of an object than to maintain its motion. Select the correct answer:

Consider the following statements regarding friction: A. Friction opposes the relative motion between two surfaces in contact. It acts only on the surface of one body. B. Friction depends on how hard the two surfaces press together. C. Static friction comes into play when we try to move an object at rest. Which of the statements given above are correct?