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': 'All are alkylating agents, except : \nSelect and explain. \nA. 5–Fluorouracil, B. Melphalan, C. Cyclophosphamide, D. Chlorambucil', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 5-Fluorouracil is an antimetabolite whereas melphalan, cyclophosphamide and chlorambucil are alkylating agents.', 'role': 'assistant'}]