MEDAL GIVEN TO CORRECT ANSWER.
When a spinning star shrinks in radius, it speeds up. Which of the following statements explains this phenomenon?

A. Circular motion is always uniform.
B. Centripetal acceleration cannot change.
C. A centripetal force always points outward.
D. Angular momentum is always conserved.

Question

MEDAL GIVEN TO CORRECT ANSWER. 
When a spinning star shrinks in radius, it speeds up. Which of the following statements explains this phenomenon?

 		A.	Circular motion is always uniform.
 		B.	Centripetal acceleration cannot change.
 		C.	A centripetal force always points outward.
 		D.	Angular momentum is always conserved.

schrodingers_cat · Answer

The answer would be D.

The conservation of angular momentum states that

$$Iw _{f} =Iw _{a}$$

As such if you decrease your moment of inertia by decreasing your radius your final angular velocity will increase because its conserved.

I hope this helps :)