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
True about drug metabolism ? 
Select and explain. 
A. Glucuronidation is phase I reaction, B. Most common enzyme involved is Cyp 3A4/5, C. Reduction is most common reaction, D. Cytochrome p450 is involved phase-II reaction
B: Most common enzyme involved is Cyp 3A4/5
Answer: B: Most common enzyme involved is Cyp 3A4/5 
Explanation: Ans. is'b'i.e., Most common enzyme involved is Cyp 3A4/5(Ref: Katzung Ilth/e p. 55)Cytochrome p450 enzymes are microsomal enzymes that are involved in phase I metabolism of many drugs.Most of the drugs are metabolized by Cyp 3A4 isoform.Cyp 3 A 4/5 carryout biotransformation of largest number (nearly 5O%) of drugs.