The answer is b. atomic bomb
Currently, about 15,000 officially cataloged objects are still in orbit. The total number of tracked objects exceeds 21,000.
When movies and television shows depict scenes of soldiers on the frontier, they should include African American actors. African American regiments frequently were sent into the Southwest and Great Plains, the most famous of which would be the Buffalo Soldiers. The Buffalo Soldiers were member of all-African American cavalry regiments who partook in many of the battle during the Indian Wars in the mid- to late-1800s.
B) People moved from cities to farms.