Concept:Population density is the number of people living in one square kilometre of land.Explanation:Population density is calculated using the formula:Population Density=Total Land AreaTotal PopulationSubstitute the given values:Population Density=500,000140,000,000Divide 140,000,000 by 500,000:=280So, the population density is 280 persons per km2.Answer:A. 280 persons per km2