A disc of mass M and radius R is rolling with angular speed o on a horizontal plane as shown. The magnitude of angular momentum of the disc about the origin O is:

• A

  $(1/2){\mathrm{MR}}^2\mathrm{\omega }$

• B

  ${\mathrm{MR}}^2\mathrm{\omega }$

• C

  $(3/2){\mathrm{MR}}^2\mathrm{\omega }$

• D

  $2{\mathrm{MR}}^2\mathrm{\omega }$