A reasonably general expression for vapour-liquid phase equilibrium at low to moderate pressure is Φ_i y_i P = Y_i x_i f_i° where, Φ 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

Answer: Option C