This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti-Cancer, Subject name: Pharmacology
[{'content': 'Mechanism of action of tacrolimus - \nSelect and explain. \nA. Folate antagonist, B. Calcineurin inhibitor, C. Antimetabolite, D. CD 20 antibody', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Calcineurin inhibitor", 'role': 'assistant'}]