Three identical masses, each of mass 1kg, are placed at the corners of an equilateral triangle of side l. Then the moment of inertia of this system about an axis along one side of the triangle is

• A

  3l²

• B

  l²

• C

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

• D

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