In the reaction where MnO4– (permanganate ion) is reduced to form Mn2+, the manganese undergoes a change in its oxidation state. The oxidation number of manganese in MnO4 is +7, and in Mn2+, it is +2.
Since the oxidation number decreases from +7 to +2, this indicates that the manganese ion is gaining electrons. A decrease in oxidation number corresponds to reduction in redox chemistry. Therefore, the manganese in MnO4 is reduced.
Thus, the correct answer is A: reduced as its oxidation number decreases.