A smooth cylinder lying on its convex surface remains A. In stable equilibrium B. In unstable equilibrium C. In neutral equilibrium D. Out of equilibrium

The correct answer is A. In stable equilibrium.

A smooth cylinder lying on its convex surface remains in stable equilibrium because if it is slightly displaced from its equilibrium position, it will tend to return to that position.

In unstable equilibrium, if the system is displaced from its equilibrium position, it will tend to move further away from that position.

In neutral equilibrium, if the system is displaced from its equilibrium position, it will neither tend to return to that position nor move further away from it.

Out of equilibrium, the system is not in a state of equilibrium.