ANS:C - anhydrous ammonia, air and water.

1. Anhydrous Ammonia: Anhydrous means "without water," so anhydrous ammonia refers to pure ammonia gas without any water content. Ammonia, with the chemical formula NH3, is a compound composed of one nitrogen atom bonded to three hydrogen atoms. It's a colorless gas with a pungent odor and is commonly used in various industrial processes, including the manufacture of fertilizers, explosives, and chemicals. In the production of nitric acid, anhydrous ammonia serves as the primary source of nitrogen for the reaction.
2. Air: Air is the mixture of gases that makes up Earth's atmosphere. It primarily consists of nitrogen (about 78%), oxygen (about 21%), and traces of other gases such as argon, carbon dioxide, and water vapor. In the context of nitric acid production, oxygen from the air is utilized as the oxidizing agent in the reaction with anhydrous ammonia to produce nitric oxide (NO), which is an intermediate compound in the overall process.
3. Water: Water, with the chemical formula H2O, is a compound composed of two hydrogen atoms bonded to one oxygen atom. It is a vital solvent and plays a crucial role in many chemical reactions. In the production of nitric acid, water is used as a reactant and as a medium for dissolving and further reacting with the nitrogen oxides (NO and NO2) formed during the initial stages of the process. These nitrogen oxides eventually react with water to form nitric acid (HNO3).

In summary, anhydrous ammonia provides the nitrogen source, air supplies the oxygen for oxidation, and water serves as both a reactant and a medium for subsequent reactions in the manufacture of nitric acid. These three components are essential for the Ostwald process, which is the primary method for nitric acid production on an industrial scale.