The value of $\mathrm{PV}$ for $5.6$ litres of an ideal gas is  $\mathrm{RT}$ at $\mathrm{NTP}$.

At $\mathrm{STP}$ the order of root mean square velocity of molecules of ${\mathrm{H}}_2, {\mathrm{O}}_2, {\mathrm{N}}_2 \& \mathrm{HBr}$ is _____.

(A) ${\mathrm{H}}_2>{\mathrm{N}}_2>{\mathrm{O}}_2>\mathrm{HBr}$
(B) $\mathrm{HBr}>{\mathrm{N}}_2>{\mathrm{O}}_2>{\mathrm{H}}_2$
(C) ${\mathrm{H}}_2>{\mathrm{O}}_2>{\mathrm{N}}_2>\mathrm{HBr}$

Enter your correct answer as A, B or C.

Between $\underset{\mathrm{A}}{{\mathrm{CO}}_2}$ and $\underset{\mathrm{B}}{{\mathrm{NH}}_3}$, the gas that will diffuse faster is _____.

Enter your correct answer as A or B.