A reasonably general expression for vapour-liquid phase equilibrium at low to moderate pressure is φi yi P = Yi xifi° where, Φ is a vapor fugacity component, Yi is the liquid activity coefficient and fi° is the fugacity of the pure component i. the Ki value (Yi = Ki xi) is therefore, in general a function of ______________________?

A. Temperature only
B. Temperature and pressure only
C. Temperature, pressure and liquid composition xi only
D. Temperature, pressure, liquid composition xi and vapour composition yi