$3 \ mol$ of ethanol reacts with $1 \ mol$ of phosphorus tribromide to give $3 \ mol$ of bromoethane and $1 \ mol$ of $X$. What is $X$?

Which of the following will not give the iodoform test?

Which one of the following is a secondary alcohol?

The number of primary isomeric alcohols with the molecular formula $C_4H_{10}O$ is:

Which of the following alcohols is most easily dehydrated with concentrated ${H_2SO_4}$?

$A$ toxic compound $A$ when reacted with $NaCN$ in aqueous acidic medium yields an edible cooking component and food preservative $B$. $B$ is converted to $C$ by diborane and can be used as an additive to petrol to reduce emission. $C$ upon reaction with oleum at $140^{\circ} C$ yields an inhalable anesthetic $D$. Identify $A, B, C$ and $D$,respectively.