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: Unknown
Which of the following statement is true regarding “Cyanide” ? 
Select and explain. 
A. Only minimally inhibits the ETC because cytochrome oxidase is the terminal component of the chain, B. Inhibits mitochondrial respiration but energy production is unaffected, C. Also binds the copper of cytochrome oxidase, D. Bind to Fe+++ of cytochrome a3
D: Bind to Fe+++ of cytochrome a3
Answer: D: Bind to Fe+++ of cytochrome a3 
Explanation: That is why methhemoglobin is an effective antidote since it also has Fe+++.
Respiration and energy production is the coupled process, so inhibition of one inhibits the other as well.
Cu is an important part of cytochrome oxidase, but cyanide does not bind it.