At a pressure of $24 \times {10}^5\mathrm{dyne} {\mathrm{cm}}^{-2}$, the volume of ${\mathrm{O}}_2$ is l0 litre and mass is 20 g. The rms velocity will be

• A

  800 ${\mathrm{ms}}^{-1}$

• B

  400 ${\mathrm{ms}}^{-1}$

• C

  600 ${\mathrm{ms}}^{-1}$

• D

  Data is incomplete