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': 'Normal values of tear film break up time range from: \nSelect and explain. \nA. 5 to 10 seconds, B. 10 to 15 seconds, C. 15 to 20 seconds, D. 15 to 30 seconds', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. 15 to 30 seconds', 'role': 'assistant'}]