A solid disc of radius 0.4 m can rotate about an axis passing through O its centre and perpendicular to the plane of the disc. Initially the disc is not rotating. Now a torque $\tau$ is applied on the disc which varies with time as shown in the figure. Then angular momentum of the disc at t = 3s is 

• A

  $12\mathrm{N}-\mathrm{m}-\mathrm{S}$

• B

  $15\mathrm{N}-\mathrm{m}-\mathrm{S}$

• C

  $10\mathrm{N}-\mathrm{m}-\mathrm{S}$

• D

  $20\mathrm{N}-\mathrm{m}-\mathrm{S}$