Methanol can be distinguished from ethanol by

$CH_3 CH_2 OH$ $\xrightarrow{Cl_2} CH_3 CHO$ $\xrightarrow{3 Cl_2} Cl_3 CCHO$. In the above reactions,the role of $Cl_2$ in step-$1$ and step-$2$ respectively is:

Which one of the following alcohols reacts instantaneously with Lucas reagent?

Among the compounds $A$ and $B$ with molecular formula $C_9H_{18}O_3$,$A$ has a higher boiling point than $B$. The possible structures of $A$ and $B$ are

$A \xrightarrow{KOBr} CHBr_3$
Here $A$ is:

Which of the following can work as a dehydrating agent for alcohols?