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
Which of the following is not a ureidopenicillin? 
Select and explain. 
A. Piperacillin, B. Mezlocillin, C. Azlocilllin, D. Flucloxacilline
D: Flucloxacilline
Answer: D: Flucloxacilline 
Explanation: None