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
Mechanism of cyanide poisoning? 
Select and explain. 
A. Inhibition of cytochrome C, B. Inhibition of complex I, C. Inhibition of carbonic anhydrase, D. Inhibition of cytochrome oxidase.
D: Inhibition of cytochrome oxidase.
Answer: D: Inhibition of cytochrome oxidase. 
Explanation: Complex IV is also called cytochrome oxidase. Inhibitors are carbon monoxide, cyanide, Hydrogen sulphide, Sodium Azide.