For an ideal solution containing a nonvolatile solute,which of the following expressions represents the vapour pressure of the solution?(where the subscripts 1 and 2 stand for solvent and solute, respectively)

Question

$\begin{array}{1 1}p=x_2p_2^*\\p=x_1p_2^*\\p=x_1p_1^*\\p_1^*-p=x_2\end{array} $