Which reducing agent is NOT commonly used in crime reduction?

Sodium chloride (NaCl) is not commonly used as a reducing agent in crime reduction because its primary role is as a salt, which is mainly utilized for purposes such as food seasoning, preservation, and various industrial applications. While it can participate in chemical reactions, it does not effectively reduce other substances.

In contrast, sodium metabisulfite, ferrous sulfate, and sulfur dioxide are all known for their reducing properties. Sodium metabisulfite is often used in various chemical processes to reduce compounds, whereas ferrous sulfate can act as a reducing agent in different situations, including water treatment. Sulfur dioxide also serves as a strong reducing agent and finds applications in various chemical reactions, including those related to crime scene investigation.

Selecting sodium chloride emphasizes its lack of common use in reduction processes, differentiating it from the other options, which are more active in reduction chemistry.