Explanation

(b)
Water and hydrochloric acid; and water and nitric acid form miscible solutions. They show negative deviation.
In case of ${CH}_{3}$ CO${CH}_{3}\$ and CHC$l_{3}$, there is interaction between them, thus force of attraction between ${CH}_{3}CO{CH}_{3}\$.. $CHCl_{3}$ is larger than between $CHCl_{3}\ldots.\$ $CHCl_{3}$ or ${CH}_{3}\$CO$Cl_{3}\ldots$ ${CH}_{3}\ CO{CH}_{3}\$and thus vapour pressure is less than expected. –a negative deviation.
In case of ${CH}_{3}\ OH$there is association by intermolecular h-bonding. When benzene is added to ${CH}_{3}OH$, H-bonding breaks and thus force of attraction between ${CH}_{3}$OH and benzene molecules is smaller than between ${CH}_{3}OH\$ or benzene molecules (in pure state).
Vapour pressure of mixture is greater than expected—a positive deviation.
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