The US Population Was 170 Million in 1950 and 240 Million

Multiple Choice

The U.S. population was 170 million in 1950 and 240 million in 1990. Assuming exponential population growth, what will the population be in the year 2020 Round your answer to the nearest million.
Select the correct answer.

A) 250 million
B) 243 million
C) 486 million
D) 972 million
E) 311 million