To create a stable population, the equation should equate the factors that contribute positively to population growth (natality and immigration) with the factors that contribute negatively (mortality and emigration).
The correct equation for a stable population is:
natality - mortality = immigration - emigration
Rearranged, this can also be expressed as:
natality + immigration = mortality + emigration.
Both forms reflect the balance needed for a stable population, but in terms of matching the responses provided, the correct one is:
natality + immigration = mortality + emigration.
This indicates that the sum of births and immigrants must equal the sum of deaths and emigrants, resulting in no net population change.