8. The world's population has grown at an average rate of 1.9 percent per year since 1945. There were approximately 4billion people in the world in 1975. Which of the

following functions represents the world's population P, in billions of people, t years since 1975? (1 billion = 1,000,000,000) \text { A. } P(t)=4(1019)^{t} \text { B. } \quad P(t)=4(19)^{t} \text { c } \quad P(t)=119 t+4 \text { D. } P(t)=1019 t+4