By the 1930s the African American population of the Midwest and Northeast had more than tripled since 1900.
had more than doubled since 1900.
had increased by half since 1900.
had remained the same since 1900.

mass production/ assembly line production

no options provided, here,but the answer to this question is often: a historian cites a japanese newspaper article published a year after the end of world war ii in order to draw conclusions about the effect of the war on the japanese economy.

clearly from the answer, the historian alludes to historical sources,and records to aid in analyzing and drawing conclusion on the effect of the war on the economy of japan.