Which of the following demographic changes can lead to a rapidly increasing population?

The choice highlighting higher birth and fertility rates is correct because these rates directly affect the growth of a population. When birth and fertility rates are elevated, it means that more individuals are being born, which contributes to a larger population in a shorter span of time. This factor results in a higher natural increase, which is the difference between the number of births and deaths within a given population.

While increased life expectancy and lower death rates among seniors can also contribute to population growth, they typically result in an aging population rather than a rapidly increasing overall population. These factors enhance the longevity of individuals rather than immediately increasing the number of births. Increased migration of older individuals, on the other hand, does not fundamentally alter birth rates and is more about population distribution than growth.

Thus, higher birth and fertility rates represent an immediate and direct mechanism by which populations can grow rapidly, making it the most significant factor in the context of the question.