Q.Choose correct option.
Haber's process is used for preparation of _______
a. HNO3 b. NH3 c. NH2CONH2 d. NH4OH

Ammonia, NH3, forms in small amounts naturally from decomposing nitrogenous organic matter, is prepared in the laboratory by decomposing an ammonium salt with a base (e.g. 2NH4Cl + Ca(OH)2 gives 2NH3 + CaCl2 + 2H2O), and is manufactured industrially by the Haber process — the direct, exothermic combination of nitrogen and hydrogen (N2 + 3H2 in equilibrium with 2NH3), favoured by high pressure (~200 atm), moderate temperature (~700 K) and an iron-oxide catalyst. It is a colourless, pungent gas, unusually high-boiling for its size because NH3 molecules hydrogen-bond to each other, and is highly water-soluble, giving an alkaline solution (NH3 + H2O in equilibrium with NH4+ + OH-) that neutralises acids to ammonium salts and precipitates many metal hydroxides from their salt solutions. Its most distinctive feature is complexation: nitrogen's lone pair coordinates to transition-metal ions, giving deep-blue [Cu(NH3)4]2+ with Cu2+ and, notably, dissolving an AgCl precipitate as soluble, colourless [Ag(NH3)2]Cl — a reaction used to identify chloride ion in qualitative analysis. Its largest industrial use is as the feedstock for fertiliser manufacture.