From amongst the following alcohols the one that would react fastest with conc, HCI and anhydrous ZNCI, 2 is (1) 1- Butanol (2) 2- Butanol (3) 2- Methylpropan -2-ol (4) 2- Methylpropanol

Lucas test in alcohols is a test to differentiate between primary, secondary and tertiary alcohols. It is based on the difference in reactivity of the three classes of alcohols with hydrogen halides.
relative reactivity of alcohol:-3>2>1
2Methyl propane 2ol is the 3 degree alcohol therefore it will react the fastest because mechanism is by carbocation formation and hence 3 degree alcohol carbocation is the most stable