From among the following alcohols, the one that would react fastest with conc.$HCl$ and anhydrous $ZnC{l}_2$ is  

The reaction of alcohol with conc. HCl and anhydrous $ZnC{l}_2$  follows $S_{N}1$  pathway, so greater the stability of carbocation formed, faster is the reaction, 2-methylpropan-2-ol gives  $3^0$ carbocation. Hence, it reacts rapidly with conc.  $HCl$ and anhydrous $ZnC{l}_2$ (Lucas reagent)