Select the correct option for the sodium-potassium pump.

• A
  Active transport of $3 Na^+$ ions out of the cell and $2 K^+$ ions into the cell.
• B
  Active transport of $3 Na^+$ ions into the cell and $2 K^+$ ions out of the cell.
• C
  Passive transport of $3 Na^+$ ions out of the cell and $2 K^+$ ions into the cell.
• D
  Passive transport of $3 Na^+$ ions into the cell and $2 K^+$ ions out of the cell.