The centripetal force is the force that provides centripetal acceleration and the resultant force that points to the center of the circle. It does not mean that the force pointing to the center of the circle must be centripetal force.

The premise of circular motion of an object with speed v is that the centripetal force of f = mv 2/r is provided by the outside world. The centripetal force is only related to the instantaneous velocity. A mistake.

Sliding friction = contact pressure * friction coefficient The pressure here can be calculated by the supporting force of the shell to the object (or the pressure of the object to the shell). There are two forces in the vertical direction: 1, supporting force 2 and gravity. Note that "centripetal force" is not an actual force, but a resultant force of external forces. Supporting force-gravity = centripetal force, so supporting force = mv 2/r+mg. So the friction force f = μ mv 2/r+μ mg. B, c is wrong.

The resultant force in the vertical direction is centripetal force, which is vertical upward. The resultant force in the horizontal direction is friction (blocking the direction of the object, but the current direction of the object is not specified in the question), so d is not sure whether it is correct. If the object moves to the right, then d is right.