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': 'Swinging flash light test is used to examine: \nSelect and explain. \nA. Cornea, B. Pupil, C. Lens, D. Conjunctiva', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Pupil', 'role': 'assistant'}]