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
Blood brain barrier is crossed by: 
Select and explain. 
A. Physostigmine, B. Neostigmine, C. Acarbose, D. All
A: Physostigmine
Answer: A: Physostigmine 
Explanation: None