Answer:
C. The rates of birth and immigration were balanced by the rates of death and emigration
.
Explanation:
A stable population size means that, over the years, number of individuals doesn't change significantly. This condition is only possible when the birth rate and immigration rate is balanced with the death rate and emigration rate. In this scenario, population size would not change much.
On the other hand, if a birth rate and immigration rate will increase, the population size in any area would be increased. This typically happens in growing cities. By contrast, if death rate and emigration rate increases, the size of population will decrease. This happens mostly in rural areas.
