It is called the is called the oxidizing agent and it gains electrons. Option C
What is the oxidizing agent?
A chemical substance that induces the electron-losing process of oxidation in another substance is known as an oxidizing agent. By taking on electrons from the substance being oxidized, the oxidizing agent itself experiences reduction in a redox (reduction-oxidation) reaction.
Put differently, the oxidizing agent aids in the oxidation of a substance that is going through a reduction process.