Astudent develops a historical argument to support this thesis: in 1950, the united states and the soviet union were two of the most powerful countries in the world. she uses the following graphic organizer to structure her argument. which answer choice could be the student's fourth source?

a. photographs of soviet missiles from 1950
b. a map of the united states in 1950
c. photographs of major u. s. cities in 1950
d. a chart showing the soviet population in 1950