Once we have calculated the oxidation numbers of different elements the next step is to figure out the oxidation and reduction half reaction. If the oxidation number of the element increases it is said t have been oxidized, and when the oxidation number of the element decreases it is said to have been reduced.
Nice question! This is a controversial topic about when or should you at all see the value reaction. I definitely feel the answer would be "C". There are quit numismatic out comes when it comes to this but I'm glad. Cheers
