In CH3‌OH and CH3‌COOH mixture solution, A−A and B−B interactions are weaker than A−B interactions. It leads to increase in vapour pressure and positive deviation Raoult's law. For solutions showing positive deviation from Raoult's law, ∆H‌mix ‌>0 and ∆V‌mix ‌>0. Thus, 1 and 4 are incorrect. According to which the correct option is (a).