b
The reagent, conc \(HCl\) and and anhydrous \(\mathrm{ZnCl}_{2}\) is Lucas reagent, which is used to distinguish between \(1^{o}, 2^{o}\) and \(3^{o}\) alcohols.

\(3^{o}\) alcohol \(+\) Lucas reagent \(\rightarrow\) Immediate turbidity.

\(2^{o}\) alcohol \(+\) Lucas reagent \(\rightarrow\) Turbidity after \(5\) mins.

\(1^{o}\) alcohol \(+\) Lucas reagent \(\rightarrow\) No reaction. Thus, the required alcohol is \(2 -\) methylpropan \(- 2 -\) ol, i.e.

\(\mathop {\begin{array}{*{20}{c}}
  {\begin{array}{*{20}{c}}
  {\,\,\,\,\,\,C{H_3}} \\ 
  | \\ 
  {{H_3}C - C - C{H_3}} 
\end{array}} \\ 
  | \\ 
  {\,\,\,\,\,OH} 
\end{array}}\limits_{({3^o}\,\,alcohol)} \)