A reasonably general expression for vapour-liquid phase equilibrium at low to moderate pressure is ? i y i P = Y i x i f i ° where, ? is a vapor fugacity component, Y i is the liquid activity co-efficient and f i ° is the fugacity of the pure component i. the K i value ( Y i = K i x i ) is therefore, in general a function of

• A. temperature only.
• B. temperature and pressure only.
• C. temperature, pressure and liquid composition x i only.
• D. temperature, pressure, liquid composition x i and vapour composition y i .