The correct answer is d. about 300 million.
In the 22nd US Census, also known as Census 2000, the population of the United States of America was 281,421,906, with an increase of 13.2% in comparison to 1990 Census. The figures of U.S. Census are based on actual counts of people living in the residential structures of USA. Certain citizens of America who are living overseas are categorically excluded during the counting irrespective of the fact that they may vote.