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 of the following is not alkylating agent? \nSelect and explain. \nA. Chlorambucil, B. Ifosfamide, C. Nitrosurea, D. Cladrabine', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Cladrabine", 'role': 'assistant'}]