Answer:
Ammonia is the richest source of nitrogen on a mass percentage basis because it has 82.35% of nitrogen by mass.
Explanation:
Percentage of element in compound :

(a) Urea, 
Molar mass of urea = 60 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 2

(b) Ammonium nitrate, 
Molar mass of ammonium nitrate = 80 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 2

(c) Nitric oxide, NO
Molar mass of nitric oxide = 30 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 1

(d) Ammonia, 
Molar mass of ammona = 17 g/mol
Atomic mass of nitrogen = 14 g/mol
Number of nitrogen atoms = 1
Ammonia is the richest source of nitrogen on a mass percentage basis because it has 82.35% of nitrogen by mass.
The answer to this statement is codein. Codein, or 3-Methylmorphine by its IUPAC name, is an opiate used as pain reliever and suppressor of coughs. Its structural formula is shown in the picture. The patient's dosage of these narcotics should be strictly prescribed by the doctor. When patients take this, they feel euphoria, hence, they tend to crave for that feeling once it's gone. Too much dosage of this drug would lead to addiction. Examples of drugs with this structural formula are Cotabflu, Nalex AC, T-Koff and Pediatuss.
When a solid (solute) comes in contact with the liquid (solvent), the solute goes about C) dissolution, in which the solid dissolves into the liquid.
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A three dimensional circular shape would be a sphere :)