What defines a reducing agent in a chemical reaction?

A reducing agent is defined as a substance that donates electrons to another substance during a chemical reaction. This process of donating electrons often leads to the reduction of the other substance, typically involving the addition of electrons or the removal of oxygen. In many reactions, the reducing agent itself gets oxidized in the process, which means it loses electrons.

In this context, the correct choice highlights that a reducing agent can take on oxygen and give away electrons. This dual characteristic is essential for identifying a reducing agent in various chemical transformations. By gaining oxygen, it can facilitate a reaction where it helps reduce other substances.

The other choices lack the comprehensive definition needed. One option inaccurately restricts a reducing agent's role to merely oxidizing other substances, which misrepresents the broader function of such agents. Another option suggests a defining characteristic that is contingent upon the formation of a product, which is not essential to the role of a reducing agent. Lastly, stating that a reducing agent remains unchanged misunderstands the concept, as reducing agents are typically transformed during the reaction, indicating their participation.