This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Drugs, Subject name: Ophthalmology
[{'content': 'A powerful cycloplegia is: \nSelect and explain. \nA. Atropine, B. Tropicomide, C. Phenylephrine, D. Homatropine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (Atorpine) (147-Parson 20th)* Atorpine - is the most potent and has longest duration of action (for 7 days or more)* Homatropine - are less potent. It affects lasts for 4-5 days* Tropicamide - short acting, though effective for upto 3 hours.* Phenylephrine - a selective alpha - 1 - agonist, sympathomimetics.', 'role': 'assistant'}]