The Civil Rights Movement was an era dedicated to activism for equal rights and treatment of African Americans in the United States. During this period, people rallied for social, legal, political and cultural changes to prohibit discrimination and end segregation.
D. is wrong. It should be "One hero in the animation field is Mel Blanc, the voice behind many cartoon characters." because the information after Mel Blanc is not necessary to the sentence. It's just extra, so you need a comma.
