Primary and secondary amines are distinguished by

Which of the following compounds gives the carbylamine reaction?

$A \xrightarrow{PhSO_2Cl} B \xrightarrow{KOH} C \xrightarrow{C_2H_5I} D$
$C$ is water-soluble.
The correct structures of $A$ and $D$ are:

Which one of the following nitro-compounds does not react with nitrous acid?

Which of the following can be used to distinguish primary,secondary and tertiary amines?

An aromatic compound "$A$" on treatment with $Zn / NH_4Cl$ and subsequent heating with ammoniacal silver nitrate solution gives a black precipitate. Which functional group does "$A$" contain?