Two equal point charges are fixed at \[x=-a\] and \[x=+a\] on the x-axis. Another point charge Q is placed at the origin. The Change in the electrical potential energy of Q, when it is displaced by a small distance \[x\] along the x-axis, is approximately proportional to [IIT-JEE (Screening) 2002]

• A.            x    
• B.            \[{{x}^{2}}\]
• C.            \[{{x}^{3}}\]                         
• D.            \[1/x\]