Three point-masses m are placed at the vertices of an equilateral triangle of side L Moment of inertia of the

system about an axis COD passing through a mass m at O and lying in the plane AOB and perpendicular to OA   as shown in the figure is

• A

  2mL²

• B

  $\frac{2}{3}{\mathrm{mL}}^2$

• C

  $\frac{5}{4}{\mathrm{mL}}^2$

• D

  $\frac{7}{4}{\mathrm{mL}}^2$