Evaluate the role of cytochrome a in the conversion of molecular oxygen into water within the electron transport chain.

• A. Cytochrome a has no role in the conversion of oxygen to water, as this process occurs independently of the electron transport chain.
• B. Cytochrome a enhances the conversion of oxygen to water, increasing the efficiency of the electron transport chain.
• C. Cytochrome a inhibits the final electron transfer to oxygen, preventing water formation and disrupting the electron transport chain.
• D. Cytochrome a facilitates the final electron transfer to oxygen, forming water and completing the electron transport chain.

Answer: (D)