A redox reaction involves which of the following?

• A. Only reduction
• B. Only oxidation
• C. Reduction and Oxidation reactions
• D. Precipitation

Answer: (C)

Redox reactions are all about electron transfer. In any redox process, the species that loses electrons is oxidized (oxidation state goes up) and the species that gains electrons is reduced (oxidation state goes down). These two processes happen together, linked by the flow of electrons from the oxidized substance to the reduced substance.

A clear example is zinc metal reacting with copper(II) sulfate. Zinc metal loses electrons and is oxidized, while the copper ions gain those electrons and are reduced. Because both oxidation and reduction occur, the overall reaction is redox.

The other ideas don’t fit because simply showing reduction would mean only gaining electrons with no source of electrons, while only oxidation would imply losing electrons with no receiver. Precipitation describes solid formation, which isn’t the defining feature of redox; redox specifically requires a change in oxidation state due to electron transfer.