One model of earth's population growth is P (t) = 64 / (1+11e^-.08t)

The question may be incomplete.

I guess the answer is as follows:

we are given the function adn we can see that when t is increased, P (t) is decreasing because of the negative sign. This means the value of the population which is the original of 64 billion will have to decrease. The answer that makes sense here is D. D. In 1990, there were 5.33 billion people.