Three closed vessels A, B and C are at the same temperature T and contain gases which obey the Maxwellian distribution of velocities. Vessel A contains only $0_2$, B only ${\mathrm{N}}_2$ and C a mixture of equal quantities of $0_2 \mathrm{and} {\mathrm{N}}_2$. If the average speed of the ${\mathrm{O}}_2$ molecules in vessel A is ${\mathrm{V}}_1$ that of the ${\mathrm{N}}_2$ molecules in vessel B is ${\mathrm{V}}_2$ the average speed of the ${\mathrm{O}}_2$ molecules in vessel C is (where M is the mass of an oxygen molecule)

• A

  $\frac{({\mathrm{V}}_1+{\mathrm{V}}_2)}{2}$

• B

  ${\mathrm{V}}_1$

• C

  ${\left({\mathrm{V}}_1{\mathrm{V}}_2\right)}^{\frac{1}{2}}$

• D

  $\sqrt{\frac{3\mathrm{kT}}{\mathrm{M}}}$