Three particles, each of mass m gram, are situated at the vertices of an equilateral triangle ABC of side l cm (as shown in the figure). The moment of inertia of the system about a line AX perpendicular to AB and in the plane of ABC, in gram cm² units will be :

• A

  2 ml²

• B

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

• C

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

• D

  $\frac{3}{4}{\mathrm{ml}}^2$