Which of the following choices is an example of "frisk" in law enforcement?

The correct choice is a protective weapons search, as this aligns with the legal definition and purpose of a "frisk" in law enforcement. A frisk is specifically a limited pat-down or search of a person's outer clothing to detect any concealed weapons or items that could pose a threat to the officer's safety. The primary goal of a frisk is to ensure the safety of the officer during an encounter by determining if the individual is carrying a weapon, while not being an invasive or thorough search.

The other options do not fit this definition. A thorough search of premises entails a more exhaustive investigation of an area or building, typically conducted under a search warrant, which is far more comprehensive than the limited scope of a frisk. Inventorying vehicle contents refers to the systematic logging of items found within a vehicle, often done during impoundment or when an arrest occurs, and does not relate to the protective purpose of a frisk. Conducting a search warrant involves authorized searches based on probable cause and is also distinctly broader in scope than a frisk, which is a precautionary measure rather than a full search.