d
Structural isomers of \(C_{3} H_{9} N\) are

\(\underbrace{\begin{matrix}
   C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}N{{H}_{2}},\,C{{H}_{3}}-CH-C{{H}_{3}}  \\
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,  \\
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,N{{H}_{2}}\,\,\,\,\,  \\
\end{matrix}}_{{{1}^{o}}\,\,amine}\)

\(C{{H}_{3}}-C{{H}_{2}}-NH-C{{H}_{3}},\)   \(\underset{{{3}^{o}}\,\,amine}{\mathop{\begin{matrix}
   C{{H}_{3}}-N-C{{H}_{3}}  \\
   |\,\,\,  \\
   \,\,\,\,C{{H}_{3}}  \\
\end{matrix}}}\,\)