In \( III ^{ rd } \) group of salt analysis for cations \( NH _{4} Cl \) and \( NH _{4} OH \) are added as group reagents. Which of the following can be used instead of \( NH _{4} Cl \) ?(a) \( NaCl \)(b) \( \left( NH _{4}\right)_{2} SO _{4} \)(c) \( \left( NH _{4}\right)_{2} C _{2} O _{4} \)(d) \( NH _{4} NO _{3} \)