Final answer:
The text develops the central idea that Marian Anderson, with the crucial support of Eleanor Roosevelt, contributed significantly to the civil rights movement through her lifelong career as a performer. THe correct option is D. Marian Anderson steadily contributed to breaking down racial barriers throughout her life and career as a performer.
Step-by-step explanation:
The central idea that is developed throughout the text is that Marian Anderson made significant contributions to the civil rights movement through her career as a performer, with the strong support of Eleanor Roosevelt.
Eleanor played a pivotal role in advocating for civil rights and took concrete actions to support African American individuals, including arranging a famous concert for Marian Anderson at the Lincoln Memorial after the DAR refused to let her perform at Constitution Hall.
Eleanor Roosevelt's consistent efforts, from arranging high-profile events to support racial equality to defying segregation laws, demonstrate that her role went beyond mere influence but was instrumental in advancing civil rights.