The formula for Nessler's reagent is:

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?

Which of the following can be detected by carbylamine reaction?

Which of the following compounds gives the carbylamine reaction?

Which of the following compounds gives a bright dye upon reaction with $NaNO_2$ in dilute $HCl$ followed by coupling with an alkaline solution of $\beta$-naphthol?

The carbylamine test is used to detect the presence of a primary amino group in an organic compound. Which of the following compounds is formed when this test is performed with aniline?