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 aEUR' 
Select and explain. 
A. 5-FU, B. Melphalan, C. Cyclophosphamide, D. Chlorambucil
A: 5-FU
Answer: A: 5-FU 
Explanation: 5 Fluorouracil Repeat from May 10 Q no.68