Which of the Following Is a Major Factor in Human

Which of the following is a major factor in human population increase in the last 200 years?

A) Humans have developed the ability to expand into almost all of the planet's climate zones.
B) Early and modern agriculture has allowed more people to be fed per unit of land area.
C) Improved health and sanitation has lowered the death rate.
D) All of these are correct answers
E) Only two of these choices are correct answers