Since the mid-1960s in the united states, select one: a. the minority population has grown faster than the white population. b. the male population has outnumbered the female population. c. the asian american population has decreased dramatically. d. fewer immigrants have been admitted than in earlier decades.

The US is becoming and more racially diverse and the reason for this is that a) there is a steady immigration and b) the minorities have more children on average - now actually less than half of the born babies is white.
So the correct option is

a. the minority population has grown faster than the white population.

the Asian American population is growing too!