Under the same $P$ and $T$,which of the following pairs of gases will diffuse at the same rate through a small jet?

$CH_4$ diffuses two times faster than a gas $X$. The number of molecules present in $32 \ g$ of gas $X$ is ($N$ is Avogadro number).

The vapor pressure of water at $80\,^oC$ is $355.5\, mm\, of\, Hg$. $A$ $100\, mL$ vessel contains $O_2$ saturated with water vapor at $80\,^oC$,and the total pressure is $760\, mm\, of\, Hg$. If the contents are transferred to a $50\, mL$ vessel at the same temperature,what will be the partial pressure of $O_2$ in $mm\, Hg$?

Two statements are given below.
Statement-$I$: Viscosity of liquid decreases with increase in temperature.
Statement-$II$: The units of viscosity coefficient are Pascal sec.
The correct answer is

At $298 \ K$, a flask '$A$' of unknown volume $(V)$ contains oxygen at $5 \ atm$. Another flask '$B$' of volume $2 \ L$ contains helium at $3 \ atm$. Two flasks are connected together by a small tube of zero volume. After the two gases are completely mixed, if the resulting mixture is found to have the mole fraction of oxygen as $0.2$, the volume of flask '$A$' (in $L$) is (Assume oxygen and helium as ideal gases)

Three layers of liquid are flowing over a fixed solid surface as shown below. The correct order of velocity of the liquid in these layers is: