Which of them is TRUE about Na –  - K+ pump: (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
Answer is B. 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.