Which statement best describes the reducing agent?

• A. It decreases the oxidation number of another atom
• B. It is the substance that gets oxidised (loses electrons)
• C. It is the electron acceptor
• D. It gains electrons

Answer: (B)

In redox processes, the reducing agent is the substance that donates electrons to another species and, as a result, is oxidized itself (its oxidation number increases). That makes the best description: it is the substance that gets oxidised (loses electrons). The other options describe effects on the other species or roles of the opposite agent: the electron acceptor is the oxidizing agent, the species that gains electrons is being reduced, and while the other substance may experience a decrease in its oxidation number, that describes what happens to the other atom, not the reducing agent itself. A simple example is zinc reducing copper(II) ions: zinc donates electrons and is oxidized, while copper(II) ions are reduced to copper.