An Isolated Object Is Initially Spinning at a Constant Speed

Multiple Choice

An isolated object is initially spinning at a constant speed. Then, although no external forces act upon it, its rotational speed increases. This must be due to

A) an increase in the moment of inertia.
B) an increase in the mass.
C) an increase in the angular momentum.
D) a decrease in the moment of inertia.
E) impossible, angular momentum conservation is violated.