# Number of electron for complete Discharge [closed]

What is the answer for question 17 and what is mean by "number of electrons for complete discharge?"

Which of the following needs the largest number of electrons for complete discharge during an electrolysis process?
a) 3 mol of $$\ce{Al^{3+}}$$
b) 4 mol of $$\ce{Al^{3+}}$$ ions
c) 5 mol of $$\ce{OH^-}$$ ions
d) 7 mol of $$\ce{O^{2-}}$$ ions

$$\text{a)} 3\times+3 = 9$$ $$\text{b)} 4\times+3 = 12$$ $$\text{c)} 5\times-1= -5$$ $$\text{d)} 7\times-2 = -14$$ This seems like an ambiguous question.