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': 'The most common site of obstruction in central retinal aery is: \nSelect and explain. \nA. In front of the lamina cribrosa, B. At the lamina cribrosa, C. Behind the lamina cribrosa, D. The point where the aery enters the optic nerve', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. At the lamina cribrosa', 'role': 'assistant'}]