An ice skater starts a spin with her arms stretched out to the sides. She balances on the tip of one skate to turn without friction. She then pulls her arms in so that her moment of inertia decreases by a factor of 2. In the process of her doing so, what happens to her kinetic energy?

• A

  It increases by a factor of 4.

• B

  It increases by a factor of 2.

• C

  It remains constant.

• D

  It decreases by a factor of 2.