# $NH_3$ can be prepared by

$\begin{array}{1 1}(a)\;Edey\;process&(b)\;Ostwald's\;process\\(c)\;Haber's\;process&(d)\;Birkland\;process\end{array}$

Haber's process :
$N_2(g)+3H_2(g) \rightleftharpoons 2NH_3+92.4KJ$
Hence (c) is the correct answer.