Final answer:
True, the angular velocity of an unsupported body can be decreased by decreasing the moment of inertia.
Step-by-step explanation:
The statement is true. The angular velocity of an unsupported body can indeed be decreased by decreasing the moment of inertia. According to the conservation of angular momentum, the angular velocity is inversely proportional to the moment of inertia. Therefore, if the moment of inertia decreases, the angular velocity must increase to conserve angular momentum. This can be illustrated with the example of a spinning figure skater pulling their arms closer to their body, causing their moment of inertia to decrease and their angular velocity to increase.