An ideal solution has two components A and B. If A is more volatile than B and also ${\mathrm{P}}_{\mathrm{A}}^{\mathrm{o}}>{\mathrm{P}}_{\mathrm{T}}$, then the correct relation between mole fraction of A in liquid (X) and vapour (Y) phase is:

According to Raoult's law,the partial pressure of a component of solution is equal to its  mole fraction in the solution multiplied by its vapour pressure in pure state.

Hence,$$\begin{gathered} {\mathrm{P}}_{\mathrm{A}}={\mathrm{P}}_{\mathrm{A}}^{\mathrm{o}} {\mathrm{X}}_{\mathrm{A} }......\left(1\right) \\ \mathrm{According} \mathrm{to} \mathrm{Dalton}\text{'}\mathrm{s} \mathrm{law},\mathrm{the} \mathrm{partial} \mathrm{pressure} \mathrm{of} \mathrm{a} \mathrm{component} \mathrm{of} \mathrm{a} \mathrm{gas} \mathrm{is}, \\ {\mathrm{P}}_{\mathrm{A}}= {\mathrm{P}}_{\mathrm{T}} {\mathrm{Y}}_{\mathrm{A}} .....\left(2\right) \end{gathered}$$  

From 1 and 2

${\mathrm{P}}_{\mathrm{A}}^{\mathrm{o}}{\mathrm{X}}_{\mathrm{A}}={\mathrm{P}}_{\mathrm{T}}.{\mathrm{Y}}_{\mathrm{A}}$

$$\begin{gathered} \mathrm{But} ,{\mathrm{P}}_{\mathrm{A}}^{\mathrm{o}} > {\mathrm{P}}_{\mathrm{T}} \\ \mathrm{Hence},{\mathrm{X}}_{\mathrm{A}}< {\mathrm{Y}}_{\mathrm{A}} \end{gathered}$$