This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2018, Subject name: Ophthalmology
[{'content': "True about Mooren's ulcer: \nSelect and explain. \nA. Painless, B. Affects cornea, C. Sudden loss of vision, D. Bilateral in majority of cases", 'role': 'user'}, {'content': "Answer: B \nExplanation: Mooren's ulcer Affects cornea Painful condition Slow loss of vision Mostly unilateral Peripheral corneal ulceration Clear cut overhanging edge seems to be melting from periphery", 'role': 'assistant'}]