This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Adverse Drug Effect, Subject name: Pharmacology
[{'content': 'Megaloblastic anemia is caused by - \nSelect and explain. \nA. Phenytoin, B. Lithium, C. Lead, D. Chloroquine', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., PhenytoinSome important drugs causing megaloblastic anaemiao Methotrexateo Phenytoino Cytosine arabinosideo Phenobarbitoneo Pentamidineo Pyrimethamineo Zidovudineo 5-Fluorouracilo Sulfasalazineo Triamtereneo Primidoneo Trimethoprimo Azathioprine", 'role': 'assistant'}]