$A$ boy is standing at the center of a turntable holding two blocks in his hands. The rotational kinetic energy of the system about the axis passing through the center is $K$. When the boy extends his arms,the moment of inertia of the system about the axis of rotation doubles. What will be the new rotational kinetic energy of the system?

• A
  $K$
• B
  $\frac{K}{2}$
• C
  $2K$
• D
  $\frac{K}{4}$