Which of the following has maximum root mean square velocity at the same temperature?

At what temperature in $^oC$ will the $rms$ speed of $CO_2$ be equal to the $rms$ speed of $CO$ at $STP$?

The r.m.s. velocity of $CO_2$ at a temperature $T$ (in kelvin) is $x \ cm \ s^{-1}$. At what temperature (in kelvin), the r.m.s. velocity of nitrous oxide would be $4 x \ cm \ s^{-1}$ (in $T$)? (Atomic weights of $C, N$ and $O$ are respectively $12, 14$ and $16$)

If the $RMS$ velocity of an ideal gas is $v \ ms^{-1}$ at $127^{\circ} C$,at what temperature its $RMS$ velocity is doubled (in $K$)?

If the $u_{rms}$ value of a gas at $27\,^oC$ is $30\,R^{1/2}$,then the molar mass of the gas is ........... $kg/mol$.

At room temperature,the average speed of helium is higher than that of oxygen by a factor of