A chloride salt on addition of alkali solution gives gas B which gives brown ppt. with Nessler's reagent. What is A, B and C?
a. NH4Cl , NH3 and HgO⋅Hg(NH2)(NO3)
b. NH4Cl , NH3 and Hg(NH2)2Cl
c. NH4Cl , NH3 and HgO⋅Hg(NH2)Cl
d. NH4Cl , NH3 and HgO⋅Hg(NH2)I