Which of the following reagents may be used to distinguish between phenol and benzoic acid?

Identify the correct set from the following:

Compound

$p K_a$

One mole of phenol is treated with dilute $HNO_3$ at $298 \ K$ to give a mixture of products. The mixture is separated by steam distillation. The steam volatile compound $(X)$ is separated. The increase in percentage of oxygen in $(X)$ with respect to phenol is . . . . . . $\times 10^{-1}$ %. (Given molar mass in $g \ mol^{-1}$: $H:1, C:12, N:14, O:16$)

Which of the following is a pair of dihydric phenols?

Sodium phenoxide when heated with $CO_2$ under pressure at $125\,^{\circ}C$ yields a product which on acetylation produces $C$. The major product $C$ would be

For phenol,which of the following statements is correct?