A thin non-conducting ring of radius R has a linear charge density $\mathrm{\lambda }={\mathrm{\lambda }}_0\cos \mathrm{\theta }$, where $\mathrm{\theta }$ is measured as shown. The total electric dipole moment of the charge distribution is

• A

  ${\mathrm{R}}^2{\mathrm{\lambda }}_0$

• B

  $2{\mathrm{\pi R}}^2{\mathrm{\lambda }}_0$

• C

  $\frac{{\mathrm{\pi R}}^2{\mathrm{\lambda }}_0}{2}$

• D

  ${\mathrm{\pi R}}^2{\mathrm{\lambda }}_0$