Final answer:
The half-reaction where electrons are reactants is known as the oxidation half-reaction, matching with option E.
Step-by-step explanation:
The half-reaction in which electrons appear as reactants is referred to as the oxidation half-reaction. In electrochemistry, an oxidation reaction is one where a substance loses electrons. During this process, the electrons are transferred to another substance, causing it to be reduced.
Therefore, the correct answer is b. E oxidation half-reaction. The confusion might stem from the fact that electrons are produced at the anode during the oxidation and consumed at the cathode during the reduction. However, the question specifically asks for the half-reaction where electrons are reactants, not the electrode where the reaction occurs.