With respect to entropy, boiling point of a solvent increases with increasing solute concentration because, as compared to the vaporization of pure solvent,

a the entropy of the "liquid phase" increases, the entropy of the vapor phase increases, and thus the amount of entropy change for the process remains the same, requiring a higher temperature to maintain the same thermodynamic favorability.

b the entropy of the "liquid phase" decreases, the entropy of the vapor phase remains the same, and thus the amount of entropy change for the process increases, requiring a higher temperature to maintain the same thermodynamic favorability.

c the entropy of the "liquid phase" decreases, the entropy of the vapor phase decreases, and thus the amount of entropy change

d for the process remains the same, requiring a higher temperature to maintain the same thermodynamic favorability. the entropy of the "liquid phase" increases, the entropy of the vapor phase remains the same, and thus the amount of entropy change for the process decreases, requiring a higher temperature to maintain the same thermodynamic favorability.