Given the balanced equation representing a reaction:
fe2o3 + 2al--> al2o3 + 2fe
during this reaction, the oxidation number of fe changes from
(1) +2 to 0 as electrons are transferred
(2) +2 to 0 as protons are transferred
(3) +3 to 0 as electrons are transferred
(4) +3 to 0 as protons are transferred

(3) +3 to 0 as electrons are transferred

Explanation: Oxidation-reduction reaction or redox reaction is defined as the reaction in which oxidation and reduction reactions occur simultaneously.

Oxidation reaction is defined as the reaction in which a substance looses its electrons. The oxidation state of the substance increases.

Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced.

For the given reaction:

On reactant side:

Oxidation state of iron = +3

Oxidation state of aluminium = 0

On product side:

Oxidation state of iron = 0

Oxidation state of aluminium = +3

The oxidation state of iron reduces from +3 to 0, it is getting reduced and it undergoes reduction reaction.