I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "The American people are mostly multi-ethnic descendants of various culturally distinct immigrant groups, many of which have now developed nations. Some consider themselves multiracial, while acknowledging race as a social construct. Creolization, assimilation and integration have been continuing processes. The African-American Civil Rights Movement (1955–1968) and other social movements since the mid-twentieth century worked to achieve social justice and equal enforcement of civil rights under the constitution for all ethnicities. In the 2000s, less than 5% of the population identified as multiracial. In many instances, mixed racial ancestry is so far back in an individual's family history (for instance, before the Civil War or earlier), that it does not affect more recent ethnic and cultural identification."? 

The mid-twentieth century social movement that addressed social justice for African-Americans began when?