Under Utah law, which of the following is true about firearm sound suppressors (silencers)?

In Utah, firearm sound suppressors, commonly known as silencers, are legal if they are registered with the ATF (B). It is important to follow the federal regulations and ensure proper registration to own and possess a firearm suppressor in the state. This is in accordance with both federal and state laws. The other options (A, C, and D) are incorrect because silencers are not illegal to own, they do not necessarily require a special state permit, and they can be used for purposes other than just hunting, although hunting might be one of the purposes for which they are commonly used.