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
[{'content': "Which one of the drugs is useful in treating Crohn's disease ? \nSelect and explain. \nA. Infliximab, B. Azathioprine, C. Tacrolimus, D. Cyclosporine", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]