What happens when the coenzyme NAD^+ gains an H atom? Multiple Choice It also gains a proton causing it to be oxidized. It loses energy. It also gains an electron causing it to be reduced. It also gains an electron causing it to be oxidized. It also gains a proton causing it to be reduced. Solution The answer will be option C . NAD+ is an oxydizing agent it accepts electron from other molecules and becomes reduced.This reaction forms NADH which can then be used as a reducing agent to donate electrons..