Answer:
Better health and nutrition were the primary reasons for rapid world population growth.
Step-by-step explanation:
The first option is correct because of the improved health because of the improvements in medicine, leading to people living much longer, and better nutrition enabled many more people to have good diets and suffer from starvation.
The second option is not correct because that would have lead to a rapid population decrease in the world.
The third option is not correct because that scenario would have led to the spread of diseases and a lot of sick people which would have resulted in a decrease in population.
The fourth option is not correct because when people have this type of lifestyle the population tends to stagnate because even though there is a high birthrate, there is also a high mortality rate.