Demographers who once believed that the U.S population would stabilize between 290 and 300 million people now believe that it will stabilize at around 390 million people because its________________?

• A. overall birth-rate will increase significantly in the early part of the new century
• B. life expectancy at birth will shortly increase to nearly 100 years of age
• C. immigration rate is expected to remain high
• D. all of the above