Which sentence is true? A. The world's population dramatically decreasing. B. Population growth in the 21th century was more than that in the 20th century. C. Population growth i...

A. The world's population dramatically decreasing.

B. Population growth in the 21^th century was more than that in the 20^th century.

C. Population growth in the 20^th century was more than that in the 21^th century.

D. In 1999, there are about 6 billion people all over the world.