This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diagnosis and Treatment of Retina, Subject name: Ophthalmology
[{'content': 'Gunn sign is? \nSelect and explain. \nA. Silver wiring of aerioles, B. Deflection of veins at aeriovenous crossing, C. Copper wiring of aerioles, D. Tapering of veins on the either side of the crossings', 'role': 'user'}, {'content': "Answer: D \nExplanation: Tapering of veins on either side of the crossings Gunn sign is seen in grade III hypeensive retinopathy. Grade 1 Generalized aeriolar attenuation Broadening of aeriolar light reflex Concealment of vein at A-V Crossings Grade 2 Severe generalized and focal aeriolar constriction A-V crossing change (Salus sign) Grade 3 Copper wiring of aerioles Venous banking distal to a-v crossing (bonnet's sign) Venous tapering on either side of the crossing (Gunn's sign) Right angle deflection of veins Flame shaped haemorrhages, cotton wool spots, hard exudates Grade 4 All changes of grade 3 Silver wiring of aerioles Disc oedema", 'role': 'assistant'}]