Answer:
The dotted line most likely represent C NADH and FADH2
Step-by-step explanation:
NADH is a reducing agent formed during glycolysis and TCA cycle. FADH2 also act as electron donor or reducing equivalent generated only during TCA cycle.
NADH and FADH2 are reduced form of coenzyme NAD+ and FAD. NADH and FADH2 formed during glycolysis or TCA cycle, enters into the electron transport chain(ETC) to perform oxidative phosphorylation that deals with reduction of oxygen(O2) to water(H2O) along with the formation of energy in form of ATP.