Amongest the given set of reactants the most appropriate for preparing $2^{\circ}$ is ____________

Question

$\begin{array}{1 1} 2^{\circ}-Br+NH_3 \\ 2^{\circ}R-Br+NaCN\;followed \;by \;H_2/pt \\ 1^{\circ}R-Br(2mol)+Potassium \;phthqlimide \;followed\;by\;H_3O^{+}/heat\\ none\;of\;these \end{array} $