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: Forensic Medicine
Cyanides shows its toxicity by binding to the following: 
Select and explain. 
A. Cytochrome oxidase, B. Acetylcholinesterase, C. Alpha adrenergic receptors, D. Histamine
A: Cytochrome oxidase
Answer: A: Cytochrome oxidase 
Explanation: Cyanide is a chemical asphyxiant; binding to cellular cytochrome oxidase, it blocks the aerobic utilization of oxygen. Whole-blood levels higher than 0.5-1 mg/L are considered toxic. The conventional cyanide antidote package consists of amyl and sodium nitrites, which produce cyanide-scavenging methemoglobinemia, and sodium thiosulfate, which accelerates the conversion of cyanide to thiocyanate. Ref: Blanc P.D. (2012). Chapter 57. Cyanide. In K.R. Olson (Ed), Poisoning & Drug Overdose, 6e.