What occurs in a redox reaction?

In a redox reaction, one of the defining characteristics is the transfer of electrons between substances. When one substance undergoes oxidation, it loses electrons, and another substance simultaneously undergoes reduction, gaining those electrons. This complementary relationship between oxidation and reduction is what makes redox reactions essential in various chemical processes, including biological systems and industrial applications.

Option C correctly reflects this concept because it emphasizes that in a redox reaction, there is always a pair of processes occurring: oxidation in one substance and reduction in another. This electron exchange is fundamental to the definition of redox reactions, indicating that the overall reaction involves changes in oxidation states of the reacting species. By understanding that both processes happen together with one substance being oxidized and another being reduced, you grasp the pivotal role redox reactions play in chemistry.