A circular loop of radius $a$, centered at origin has five positive charges equally spaced on it. All charges have a magnitude Q , except the one at $(0, a)$ which has a magnitude $q$, as shown in the figure. The electric field at the origin will be

• A

  $\frac{1}{4 \pi \epsilon_0}\left[\frac{4 Q+q}{a^2}\right] \hat{j}$
• Correct answer
  B

  $\frac{1}{4 \pi \epsilon_0}\left[\frac{Q-q}{a^2}\right] \hat{j}$
• C

  $\frac{1}{4 \pi \epsilon_0}\left[\frac{4 Q}{a^2} \sin \left(\frac{2 \pi}{5}\right)+\frac{q}{a^2}\right] \hat{j}$
• D

  $\frac{1}{4 \pi \epsilon_0}\left[\frac{4 Q}{a^2} \cos \left(\frac{2 \pi}{5}\right)+\frac{q}{a^2}\right] \hat{j}$

Hence, the correct answer is option: 'B'.