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 one of the following alkaloids is used as anti–cancer agent ? 
Select and explain. 
A. Vincristine, B. Papaverine, C. Ephedrine, D. Atropine
A: Vincristine
Answer: A: Vincristine 
Explanation: None