The sodium-potassium pump within living cells requires energy to move ions across the cell membrane
 to maintain homeostasis. How is this energy supplied?
 A When adenine is removed from adenosine triphosphate (ATP), a large amount of energy is
 produced.
 B When two adenosine triphosphate (ATP) molecules are fused together, a large amount of energy
 is produced.
 C When a phosphate group is removed from adenosine triphosphate (ATP), a large amount of energy
 is produced.
 D When the sugar and phosphate groups of adenosine triphosphate (ATP) are fused together, a
 large amount of energy is produced.