Cytochrome C is responsible for accepting the electrons generated in the bc1 complex (complex III) and transferring them over to complex IV. In other words, cytochrome C oxidizes complex III and is oxidized by complex IV. This is required to then add those electrons to molecular oxygen, which forms water and contributes to the proton gradient required for ATP production. 

The final electron acceptor in the electron transport chain is oxygen gas. one oxygen gas molecule will accept 4 electrons and combine with 4 protons in order to create 2 water molecules. This reaction is the reason water is a byproduct of aerobic cellular respiration.

Glycolysis, the first step in metabolism of carbohydrates, occurs in the cytoplasm. The products of glycolysis (pyruvate and NADH) are transported to the mitochondrial matrix. The products undergo series of reactions called the Krebs cycle. The products of Krebs cycle and NADH from glycolysis enter the inner mitochondrial membrane and go through the electron transport chain (ETC). During ETC, oxidative phosphorylation generates most of the ATP used by the cells.

Reduction is the process of gaining electrons. In electron transport chain (ETC), electron carriers such as NADH and  donate electrons to the electron carriers in the ETC. These electrons are transported to subsequent molecules. The final acceptor of electrons in ETC is oxygen, which accepts electrons and gets converted into water. Since electrons are being lost from them, NADH and  are oxidized in the ETC. On the other hand, oxygen accepts electrons and is reduced in the electron transport chain.

The question states that oligomycin inhibits ATP synthase. Recall that ATP synthase (found on the inner mitochondrial membrane) generates ATP by transporting protons from the intermembrane space (space between inner and outer mitochondrial membrane) into the mitochondria. Inhibiting this will prevent the transport of protons and will, subsequently, lead to a buildup of protons in the intermembrane space.

Proton pumps are also found on the inner mitochondrial membrane. They function to pump out protons from the inside of mitochondria to the intermembrane space, thereby providing the proton gradient for ATP synthase to generate ATP. Halting ATP synthase will cause proton pump to stop pumping protons into the intermembrane space (due to the increase in protons in intermembrane space).

ATP synthase is the major generator of ATP; therefore, halting ATP synthase via oligomycin will decrease the amount of ATP generated.

The F0 subunit of ATP synthase is where protons flow through to create ATP. This mechanism involves a rotation of the subunit, producing ATP with each turn. ATP synthase is part of oxidative phosphorylation, the greatest ATP producing segment of cellular respiration.

Electrons flow throughout the electron transport chain via redox reactions. They flow from the most negative voltage to the most positive voltage within the chain. Thus the correct flow would be from C (most negative) to B (Less negative) to A (most positive).

Photosystems I and II are each capable of conducting electrons, with photosystem II handing off electrons to photosystem I. This is accomplished by the electron carrier molecule plastocyanin. 

Photosystems I and II are responsible for the light-dependent reactions of photosynthesis. These two photosystems work in tandem to create ATP and NADPH products. ATP is created in photosystem II, while NADPH is created in photosystem I.

Excitation of photosystem II splits water in the thylakoid space into hydrogen and oxygen. The hydrogen then passes through ATP synthase to move down its concentration gradient and into the stroma. Excitation of photosystem I passes electrons to NADP⁺ reductase to convert NADP⁺ to NADPH. Regeneration of NADPH is necessary for the Calvin cycle.