The Human Population's Life Expectancy Has Increased Significantly but Seems

The human population's life expectancy has increased significantly but seems to have an upper limit. Which of the following might be described as an ecological consequence of passing that upper limit by regulating cell death?

A) an increase in the relative frequency of deaths from cancer
B) an increased need for gerontologists and other professionals to care for the elderly
C) an increase in the total population of humans on the planet
D) a decrease in the ratio of younger to older members of the population
E) a decrease in the birth rate