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': 'Unit of light emitted from a surface is: \nSelect and explain. \nA. Lambe, B. Candella, C. Lux, D. Lumen', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. LumeLumen', 'role': 'assistant'}]