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: Ophthalmology
Selective alpha 2 agoinst used in glaucoma ? 
Select and explain. 
A. Tirriolol, B. Epinephrine, C. Dipivefrine, D. Brimonidine
D: Brimonidine
Answer: D: Brimonidine 
Explanation: Ans. is 'd' i.e., Brimonidine