Final answer:
Most future population growth in developed countries will be due to natural increase from past high fertility, and migration will be an inevitable consequence of the recent changes in fertility.
Step-by-step explanation:
The correct answer is c) Natural increase, migration. In developed countries, most future population growth will be due to natural increase, which refers to the difference between the number of births and deaths. This growth is a result of past high fertility rates in these countries. Migration, on the other hand, is the movement of individuals from one place to another, and it will be an inevitable consequence of the recent changes in fertility. As birth rates decline in developed countries, immigration becomes an important factor for population growth.