OILRIG. oxidation is loss of electron while reduction is the gain. oxidizing agents oxidize to be reduced while reducing agents reduce to be oxidized. reducing agents donate electrons.
Heres a handy rhyme: OIL RIG Oxidation Is Loss of electrons (donates) Reduction Is Gain of electrons (accepts/receives) In this instance, we are looking for the substance that gets oxidized. The Reducing agent CAUSES reduction, but it itself get oxidized. therefore youre looking at c, the reducing agent