Partial pressure of ethanol $=4.556 \,kPa$
Total pressure $=$ Partial pressure of methanol $+$ Partial pressure of ethanol
Total pressure $=2.619+4.556=7.175\, kPa$
$X _{\text {methanol: }}$ : Mole fraction of methanol
$X _{\text {ethanol: }}$ : Mole fraction of ethanol
The partial pressure of methanol $= X _{\text {methanol }} \times$ Total pressure
$\therefore X _{\text {methanol }}=\frac{2.619}{7.175}$
$=0.365$
$\therefore$ Mole fraction of ethanol $= 1 -$ Mole fraction of methanol
$=1-0.365$
$=0.635$
Hence, the correct option is $B$.
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Acetoacetic ester $\xrightarrow{NaOEt}$ $\xrightarrow{C{{H}_{3}}I}$ $\xrightarrow{NaOEt}$ $\xrightarrow{C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}Br}$