The major product obtained on interaction of phenol with sodium hydroxide and carbon dioxide is

Which of the following compounds is least likely to give effervescence of $CO_2$ in the presence of aqueous $NaHCO_3$?

In the given reaction,$[X]$ will be:
$2\text{-hydroxybenzoic acid} \rightarrow{200^{\circ}C} [X]$

The major product of the following reaction sequence is

Given below are two statements :
Statement $I$ : Picric acid is $2,4,6$-trinitrotoluene.
Statement $II$ : Phenol-$2,4$-disulphonic acid is treated with conc. $HNO_3$ to get picric acid.
In the light of the above statements,choose the most appropriate answer from the options given below :

The most suitable method for the separation of a $1:1$ mixture of $o-$ and $p-$ nitrophenols is: