Answer:
The correct answer is c. Difference between the birth rate and death rate.
Explanation:
The natural growth rate of the population on a worldwide, country, region or city scale is produced on the difference between two demographic facts, the entry of new population to the existing one (birth rate), to the opposite one, which the population output must be subtracted, (death rate). The population is currently growing because there are more births than deaths, while in the historical moments in which it has descended it was because there were more deaths than births.
Formula
Natural Growth rate = (Birth rate - Death rate)/10