The half of an oxidation-reduction reaction shows the iron gains. what does this electron gain mean for iron.

The correct answer is option C, that is, it is reduced.

In reduction and oxidation reactions, reduction refers to the loss of an oxygen atom from a molecule or the gaining of one or more electrons. A reduction reaction is observed from the perspective of the molecule being reduced, as when one molecule gets reduced, another one gets oxidized. The complete reaction is called a redox reaction.

In the given case, iron gains electrons mean that it is reduced.  

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i think it's c. i'm not sure but i think so.