The correct answer is D) African Americans.
Even though African American citizens contributed to the war effort abroad and at home, they still faced widespread discrimination in the US. Public facilities were still largely segregated, African Americans were limited in the places where they could live, and continually faced violence in the South by members of the KKK. This lack of support after helping the US in the war and the constant mistreatment helped to spark the Civil Rights movement of the 1950's and 1960's.
