In a regular polygon of n sides, each comer is at a distance r from the centre. Identical charges each of magnitude q are placed at comers. The field at the centre is

• A

  $\left(\frac{\mathrm{n}}{\mathrm{n}-1}\right)\mathrm{k}\frac{\mathrm{q}}{{\mathrm{r}}^2}$

• B

  $\left(\frac{\mathrm{n}-1}{\mathrm{n}}\right)\mathrm{k}\frac{\mathrm{q}}{{\mathrm{r}}^2}$

• C

  0

• D

  $(\mathrm{n}-1)\mathrm{k}\frac{\mathrm{q}}{{\mathrm{r}}^2}$