a
Note : In the given reaction a molecule of \(HCl\) is lost and \(C\, = C\) double bond is formed. Thus it is dehydrohalogenation reaction . Nitro group is electron withdrawing group. Hence increases the acidity of \(H\) atom ( attached to \(C\) atom bearing nitro group) which is removed easily. Further the newly formed double bond is in conjugation with nitro group \([Figure\,1]\)\(\xrightarrow[{Heat}]{{NaOC{H_3}\left( {1\,eq.} \right)}}\) \([Figur\,2]\)