Which among the following represent reagent ' A '?

2- Naphthol aniline dye is a scarlet dye that can be prepared by coupling reaction. Aniline reacts with sodium nitrite in the presence of hydrochloric acid to form benzene diazonium chloride. Further benzene diazonium chloride reacts with 2-naphthol forms a bright orange colour 2-naphthol and forms aniline dye.