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
True about Na+ - K+ pump is that 
Select and explain. 
A. Involves ATPase activity, B. It can move Na+ in and out of cell, C. Electrically neutral, D. Pumps out one Na+ for one K+
A: Involves ATPase activity
Answer: A: Involves ATPase activity 
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.