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: Biochemistry
Daily vitamin A intake 
Select and explain. 
A. 1000 I.U, B. 2000 I.U, C. 3000 I.U, D. 4000 I.U
D: 4000 I.U
Answer: D: 4000 I.U 
Explanation: None