In esterification,the reactivity of alcohols is:

$A$ 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.

What is the major product of the following reaction?

Which of the following compounds does $NOT$ respond positively to the iodoform test?

Which of the following compounds will give the iodoform test?

Which of the following gives a negative iodoform test?