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
[{'content': 'Which is the shoest acting mydriatic? \nSelect and explain. \nA. Tropicamide, B. Atropine, C. Phenylephrine, D. Hyoscine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Tropicamide is the quickest (20-40min) and shoest acting (3-6hours) mydriatic. Atropine is a potent mydriatic but its slow and has long lasting action. With it, pupil dilates in 30-40min but cycloplegia takes 1-3hours.', 'role': 'assistant'}]