Which statement about hispanic immigration to the u. s. during the 1990s is true?
a. hispanic immigration has caused the u. s. population center to shift from missouri to california.
b. the number of hispanics in the u. s. remains far lower than the number of african americans.
c. most hispanic immigrants don't remain in the u. s. because they can't speak english.
d. the hispanic population in the u. s. more than doubled between 1990 and 2000.