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
The α2 agonist used in glaucoma is: 
Select and explain. 
A. Guanacare, B. Guanabenz, C. Brimonidine, D. Tizanidine
C: Brimonidine
Answer: C: Brimonidine 
Explanation: None