When an Object Is Effectively Isolated from External Torques, Like

When an object is effectively isolated from external torques, like an ice skater twirling on the tip of one skate, the angular momentum of the object

A) can be increased by shifting mass out away from the axis of rotation.
B) can be decreased by shifting mass out away from the axis of rotation.
C) can be increased by shifting mass in toward the axis of rotation.
D) can be decreased by shifting mass in toward the axis of rotation.
E) cannot be changed except by friction at the point of contact.