Ethanol reacts with Lucas reagent (conc. HCl + anhydrous ZnCl2) to form a cloudy or turbid solution due to the formation of an alkyl chloride.

The reaction occurs as follows:

\[ \text{CH}_3\text{CH}_2\text{OH} + \text{HCl} \xrightarrow{} \text{CH}_3\text{CH}_2\text{Cl} + \text{H}_2\text{O} \]

This reaction is a typical test for the presence of a primary or secondary alcohol. Primary alcohols react slowly with Lucas reagent and may not produce a turbid solution immediately. However, secondary alcohols react more readily and form turbidity faster.

Therefore, the correct answer is likely option (b) After 5 to 7 mins, as this timeframe is typical for the turbidity to become apparent with ethanol.