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 of the following drugs are components of the MOPP cancer Chemotherapy regimen EXCEPT: 
Select and explain. 
A. Procarbazine, B. Vincristine, C. Mechlorethamine, D. Methotrexate
D: Methotrexate
Answer: D: Methotrexate 
Explanation: None