Uhm u should know its by pollen thats transferred by bees so asexually>
I think the correct term to fill in the blanks would be glycerol phosphate electron shuttle. This shuttle is responsible of transporting agents that are reducing into the inner membrane of the mitochondria. Since NADH cannot enter, it is reduced so that the electrons could go in to the transport chain.
I believe the answer is B - point source comes from a specific site, non-point comes from many sources