$\begin{array}{1 1}\text{Plot of }p_{total}\text{ versus }y_A\text{ (mole fraction of A in vapour phase) is linear}\\\text{Plot of }p_{total}\text{ versus }y_B\text{ is linear}\\\text{Plot of }1/p_{total}\text{versus }y_A\text{ is linear} \\\text{Plot of }1/p_{total}\text{versus }y_B\text{ is linear} \end{array} $