This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory chain, Subject name: Biochemistry
Which of the following inhibit complex IV? 
Select and explain. 
A. Amylobarbital, B. Aconitase, C. Secobarbitone, D. Cyanide
D: Cyanide
Answer: D: Cyanide 
Explanation: Site-III (Complex IV) * Cyanide Blocks electron transfer from cyt b to c1 Inhibits terminal * H2S * Azide transfer of electrons to molecular O2 * Co (Carbon monoxide): Inhibits Cyt. oxidase by combining with O2 binding site. It can be reversed by illumination with light.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th edition, page no: 143