An electric dipole $\overrightarrow{P}=\frac{p}{\sqrt{2}}\left(\widehat{i}-\widehat{j}\right)$  is placed at the origin. Then the angle between electric field vector $\overrightarrow{E}$  at point (a, a) and the positive x-axis is

• A

  ${30}^o$

• B

  ${45}^o$

• C

  ${135}^o$

• D

  ${120}^o$