According to Raoult's law, for a component of an ideal binary solution the partial vapour pressure is

Aequal to its mole fraction in the vapour multiplied by the total pressure of the pure component
Binversely proportional to its mole fraction in the liquid
Cequal to the vapour pressure of the pure component divided by its mole fraction
Dequal to its mole fraction in the liquid multiplied by the vapour pressure of the pure component

Answer: D

Raoult's law states

p_{i} = x_{i} p_{i}^{0}

, with

x_{i}

the mole fraction in the liquid phase and

p_{i}^{0}

the vapour pressure of pure

i

. The other options either use the wrong phase or invert the proportionality.