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
All are alkylating agents, except : 
Select and explain. 
A. 5–Fluorouracil, B. Melphalan, C. Cyclophosphamide, D. Chlorambucil
A: 5–Fluorouracil
Answer: A: 5–Fluorouracil 
Explanation: 5-Fluorouracil is an antimetabolite whereas melphalan, cyclophosphamide and chlorambucil are alkylating agents.