Electricity is added to recharge a battery. what is added to adp to form atp? a.) a second ribose group b.) a third phosphate group c.) a third ribose group d.) a second phosphate group

The correct answer would be option B. A third phosphate group. Since ADP means  Adenosine "diphosphate"--having two phosphate groups, so in order to create three phosphate groups, which would then result in Adenosine "Triphosphate" (Tri= three) , a third phosphate group should be added. 

The correct answer is d