Oxidative phosphorylation occurs during

a. The electron transport chain

b. Formation of NADH

c. Formation of FADH2

d. Formation of CoA from acetyl CoA

The correct answer will be option-A.

Explanation:

Oxidative phosphorylation is a process which leads to the formation of ATP molecule. During oxidative phosphorylation, the transfer of electrons from reducing equivalents like NADH and FADH₂ formed during cellular respiration to oxygen leads to the formation of ATP.

Since oxidative phosphorylation involves the transfer of electrons from these equivalents through the electron transport chain which takes place in the inner membrane space of mitochondria. Therefore, oxidative phosphorylation and electron transport chain are interlinked.

Thus, option-A is the correct answer.