c
Among the given  statement only \((c)\) is true. As methyl amine liberates \(N_2\) on reaction with nitrous acid.

\(C{{H}_{3}}-N{{H}_{2}}+2HONO\,\to C{{H}_{3}}-ONO+{{N}_{2}}+2{{H}_{2}}O\)

while dimethylamine and trimethyl amine form insoluble compound with hinsberg reagent and \(KOH\).

\({{R}_{2}}NH\,+\,{{C}_{6}}{{H}_{5}}S{{O}_{2}}Cl\,\xrightarrow{O{{H}^{-}}}\) \({{C}_{6}}{{H}_{5}}S{{O}_{2}}N{{R}_{2}}\)

\({{R}_{3}}N\,+\,{{C}_{6}}{{H}_{5}}S{{O}_{2}}Cl\,\xrightarrow{O{{H}^{-}}}\underset{insoluble}{\mathop{{{R}_{3}}N}}\,\)

Azo dyes are not formed by secondary amines.