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 retinal capillaries are distinguished by having all, except: \nSelect and explain. \nA. Widening of the capillary calibre in the periphery, B. Capillary free zone around the veins, C. Superficial network, D. Deep denser network', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Capillary free zone around the veins', 'role': 'assistant'}]