This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the component of respiratory chain reacts directly with molecular oxygen ? 
Select and explain. 
A. Cyt b, B. CoQ, C. Cyt C, D. Cyt aa3
D: Cyt aa3
Answer: D: Cyt aa3 
Explanation: Ans. is 'd' i.e., Cyt aa3