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 drug is used in Alzheimer's disease : 
Select and explain. 
A. Tacrine, B. Pemoline, C. Doxapram, D. Methylphenidate
A: Tacrine
Answer: A: Tacrine 
Explanation: None