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
Which of them is TRUE about Na –  - K+ pump 
Select and explain. 
A. K+ is pumped against the gradient, B. 2K+ are exchanged with 5Na+, C. Hypercalcemia causes arrest in Na+ K+ pump, D. Increase in intracellular Na+ increases action potential
B: 2K+ are exchanged with 5Na+
Answer: B: 2K+ are exchanged with 5Na+ 
Explanation: In Na+-K+ exchange, 3 Na+ goes out and 2K+ goes into the cell with the utilization of ATP. 
Hence it is a primary active transport. Due to the net flow of Na+ outwards, there is a potential difference that occurs. Both Na+  and K+  are pumped against a concentration gradient by using ATP.