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': 'Peripheral anterior synechiaeafteran attackof acute congestive glaucoma occur earliest in the: \nSelect and explain. \nA. Lower pa, B. Upper pa, C. Lower and inner pa, D. Lower and outer pa', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Upper pa', 'role': 'assistant'}]