As per this diagram a point charge y + q is placed at the origin O. Work A done in taking another point charge - Q from the point A (0, a) to another point B (a, 0) along the straight path AB is :

• A

  $\left(\frac{-\mathrm{qQ}}{4{\mathrm{\pi \epsilon }}_0}\right)\sqrt{2}\mathrm{a}$

• B

  Zero

• C

  $\left(\frac{\mathrm{qQ}}{4{\mathrm{\pi \epsilon }}_0}\frac{1}{{\mathrm{a}}^2}\right)\frac{1}{\sqrt{2}}$

• D

  $\left(\frac{\mathrm{qQ}}{4{\mathrm{\pi \epsilon }}_0}\frac{1}{{\mathrm{a}}^2}\right)\sqrt{2}\mathrm{a}$