For a binary mixture at constant temperature and pressure, which of the following relation between activity coefficient (i) and mole fraction (xi) obeys the Gibbs - Duhem equation for a thermodynamically consistent system? Justify your answer A) ln 1 = -1+2x1-x1 2 ; ln 2 = - x1 2 B) ln 1 = -1+2x1-x1 2 ; ln 2 = x1 2