Help please.

B. It is happening today in the united states and europe.C. its happening today in most developing nations.D. Occured in the U.S and europe in the 19th century.

Explanation:

The demographic transition the movement of the population from a high birth and high death rate to low birth and low death rate of population growth.  It began in the 19th century in the economically developed nations of the world.  A large reduction in birth rates was followed by the early 20th century.  The developing nations of the world are having large-scale population growth while the developed are declining.

Ibelieve the answer is c also i'm in k12 too

1. antarctica2. saudi arabia