Which statement is true regarding a reducing agent?

A reducing agent is a substance that donates electrons to another substance in a chemical reaction, resulting in the reduction of that substance. During this process, the reducing agent itself undergoes oxidation, meaning it loses electrons. This dual process—where the reducing agent donates electrons and is oxidized—highlights the essential role of reducing agents in redox (reduction-oxidation) reactions.

In a typical redox reaction, as the reducing agent donates electrons, it often corresponds to an increase in oxidation state. In contrast, the substance receiving the electrons (the oxidizing agent) undergoes reduction, which means it gains electrons and decreases in oxidation state.

Among the other possible choices, the statement regarding the necessity of a solid substance for a reducing agent is not valid, as reducing agents can be gases, liquids, or solids. The assertion that a reducing agent must increase reaction temperature is also incorrect, as temperature changes are not inherently linked to the role of reducing agents in reactions. Finally, characterizing a reducing agent as one that gets reduced during the reaction is directly contradictory to its definition, as a reducing agent is oxidized while reducing another species.