Final answer:
The factor not contributing to rapid population growth is the Increase in illiteracy. Education typically leads to lower birth rates, whereas public health advancements like vaccines contribute to population growth by reducing mortality.
Step-by-step explanation:
The option that is not a factor contributing to rapid population growth in the world is D. Increase in illiteracy.
Explanations for the rapid population growth include significant advances in public health, such as improvement in knowledge regarding hygiene, the development of antibiotics and vaccines, and actions to control diseases. These advancements have led to a decline in mortality rates and enhanced the ability of societies to sustain larger populations.
Conversely, an increase in illiteracy does not contribute to population growth, as it does not directly affect human life expectancy or reproductive rates. Instead, education is often correlated with lower birth rates as it leads to improved family planning and access to health services.