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: Pharmacology
All of the following enzymes and their reactions are involved in the metabolism of Xenobiotics, EXCEPT: 
Select and explain. 
A. Cytochrome oxidase, B. Cytochrome p 450, C. Methylation, D. Hydroxylation
A: Cytochrome oxidase
Answer: A: Cytochrome oxidase 
Explanation: Cytochrome oxidase is not mentioned as an enzyme in the metabolism of xenobiotics but Cytochrome P450 and Hydroxylation reactions are involved in Phase-1 metabolic reactions and Methylation forms a pa of phase II reactions. Ref: Harpers Biochemistry, 27th Edition, Page 633; Lippincott's Illustrated Reviews: Pharmacology, 4th Edition, Page 14; Goodman and Gilman's The Pharmacological Basis of Therapeutics, 11th Edition, Page 44