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: Physiology
Na+ – K+ ATPase 
Select and explain. 
A. 3 Na+ out/ 2K+ in, B. 3Na+ in/ 2K+ out, C. 2Na+ out/ 3K+ in, D. 2Na+ in/3K+ out
A: 3 Na+ out/ 2K+ in
Answer: A: 3 Na+ out/ 2K+ in 
Explanation: In Na+-K+ exchange, 3 Na goes out and 2K goes in to the cell.