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
Tear film break-up-time is the time: 
Select and explain. 
A. Between the last blink and the appearance of first dry spot on the cornea, B. Taken for appearance of dry spot between two blinks, C. Taken by successive blinks to break the tear film, D. Taken for disappearance of dry spots on the cornea
A: Between the last blink and the appearance of first dry spot on the cornea
Answer: A: Between the last blink and the appearance of first dry spot on the cornea 
Explanation: Ans. Between the last blink and the appearance of first dry spot on the cornea