Anil has noticed that infertility has been affecting many of his intergenerational friends and family. Based on this observation, Anil is writing his senior thesis on the effects that certain cities, water quality, and hormones might have on his friends. Anil will most likely approach his findings and paper using which theory?
a. Demographic transition theory
b. Cornucopian theory
c. Zero population growth theory
d. Malthusian theory

Zero population growth occurs when there is no increase and decrease within the population. The population at this level is balanced because the number of people isn't growing and isn't decreasing. This means mortality rate is equal to fatality rate also immigration is equal to migration.

Which means people who are born each year are equal to people who die that year; same as the number of people who leave the country is equal to the number of people who enters into the country. It is vital for population stability and sustainability of the available resources which are rapidly getting outstripped by the rate of population growth.

Some countries have concerned about rapidly population growth in such that they have stipulated the number of babies born per person just to maintain population stability.