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': 'A 24 year old man on physical examination was noted to have ptosis. Which of the following muscle must be paralyzed? \nSelect and explain. \nA. Orbicularis Oculi, lacrimal pa, B. Orbicularis Oculi, palpebral pa, C. Superior tarsal, D. Superior oblique', 'role': 'user'}, {'content': "Answer: C \nExplanation: The superior tarsal muscle is a smooth muscle which is sympathetically innervated. It is an involuntary muscle that elevates the eyelid. It is innervated by the cervical sympathetic trunk, and this muscle's functioning provides a good indication of the integrity of the cervical sympathetic trunk. If the cervical sympathetic trunk has been damaged, a patient will have ptosis, a droopy eyelid.", 'role': 'assistant'}]