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 is a pro-drug? 
Select and explain. 
A. Cyclophosphamide, B. Lisinopril, C. Metochlopramide, D. Ranitidine
A: Cyclophosphamide
Answer: A: Cyclophosphamide 
Explanation: Ans. is 'a' i.e., Cyclophosphamide