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
In a patient taking oral contraceptive, the chance of pregnancy increases after taking any of the following drugs except - 
Select and explain. 
A. Phenytoin, B. Griseofulvin, C. Ampicillin, D. Cimetidine
D: Cimetidine
Answer: D: Cimetidine 
Explanation: Ans. is 'd' i.e., Cimetidine