The correct responses are:
A - President Harry Truman issued an executive order to integrate the United States military.
B - The Voting Rights Act of 1965 helped to expand the participation of Americans in the political process.
C - The Supreme Court ruled in Brown v. Board of Education that the practice of segregation in public schools was illegal.
D is incorrect because the Civil Rights Act of 1964 did not address gerrymandering or make it illegal; it focused on prohibiting discrimination based on race, color, religion, sex, or national origin.