What is the key characteristic of an oxidation–reduction reaction?
A.
Electricity is gained.
B.
Electricity is lost.
C.
Electrons are exchanged.
D.
Electrons are gained.
E.
Electrons are lost.

C. Electrons are exchanged

Explanation:

Oxidation-Reduction reaction (Redox) is a type of chemical reaction in which there is a transfer of electrons between the reacting substance.

In this type of reaction, one of the reacting substance, called the Reducing  Agent, undergoes Oxidation (loss of electrons), while the other reacting substance, called the Oxidising Agent ,undergoes Reduction (gains electron).