Mole fraction is useful in relating vapor pressure with the concentration of a solution.

According to Raoult’s law, the partial vapor pressure of each component in the solution is directly proportional to its mole fraction.

Thus, for a component C in a solution

Where P_C is the partial pressure of component C and x_c is a mole fraction of C in a solution.

Thus, option (i) is corerect and others are wrong.