An aqueous solution of a salt has basic nature. What are the types of acid and base from which this salt is formed?

Four students $\mathrm{a}, \mathrm{b}, \mathrm{c}$ and $\mathrm{d}$ of class $\mathrm{X}$ measured the pH values of the given samples of distilled water, $0.1 \mathrm{M}$ solution of ethanoic acid, $0.1 \mathrm{M}$ solution of hydrochloric acid and $0.1 \mathrm{M}$ solution of sodium hydroxide using pH papers at $298 \mathrm{K}$. Tell which one of the following represents a correct measurement?