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
True about cornea: 
Select and explain. 
A. Power is 43 D, B. Majority of refraction occur at air-tear interface, C. With the rule astigmatism is present because veical meridian more sleep than horizontal meridian, D. All
D: All
Answer: D: All 
Explanation: Ans. All A, B and C