Whenever a substance is oxidized,

Question

Quizplus · Accepted Answer

When a substance is oxidized, it loses electrons. In order for this to happen, another substance must gain those electrons through reduction. Therefore, whenever a substance is oxidized, some other substance must be reduced.

The other choices are incorrect as:
A) the substance that causes the oxidation is called the oxidizing agent, not the substance that is oxidized itself. 
C) when a substance loses electrons, it is undergoing oxidation, not gaining electrons. 
D) hydronium ions are not always produced during oxidation.

Whenever a Substance Is Oxidized