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 the following increases drug metabolism by activating cytochrome enzyme, EXCEPT: 
Select and explain. 
A. Tetracycline, B. Cimetidine, C. Rifampicin, D. Phenobarbitone
B: Cimetidine
Answer: B: Cimetidine 
Explanation: None