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 value of tear film break-up time \nSelect and explain. \nA. 5-10 seconds, B. 10-15 seconds, C. 15-30 seconds, D. > 35 seconds', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Tear Film break-up time:\nIt is the interval between a complete blink and appearance of first randomly disributed dry spot on the cornea.\nNormal value - 15-35 seconds.', 'role': 'assistant'}]