Answer
(b) 9 times.
Work Step by Step
Electrostatic potential energy
$E_{el}\propto\frac{Q_{1}Q_{2}}{d}$
$\implies\frac{E_{el}\,where\,charges\,are\,+3\,and\,-3}{E_{el}\,where\,charges\,are\,+1\,and\,-1}=\frac{k\frac{(+3)(-3)}{d}}{k\frac{(+1)(-1)}{d}}$
$=9$
$E_{el}$ between charges of +3 and -3 is 9 times that between charges of +1 and -1. Therefore, the correct option is (b).
