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': 'An elderly male with heart disease presents with sudden loss of vision in one eye; examination reveals cherry red spot; diagnosis is – \nSelect and explain. \nA. Central retinal vein occlusion, B. Central retinal artery occlusion, C. Amaurosis fugax, D. Acute ischemic optic neuritis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Amongst the given options only CRAO causes sudden painless loss of vision along with cherry red spot.', 'role': 'assistant'}]