The third alternative is correct (C).
The march to Washington was seen as a milestone in the struggle for equal civil rights for black Americans.
Although the American Constitution guaranteed fundamental rights to all American citizens since 1987, for many years blacks had different legal conditions from whites. There was strong racial segregation in the country, which divided access to public and private places between whites and blacks, including bathrooms, transportation, housing and employment opportunities.
In 1963, Martin Luther King led the March on Washington, which hailed the end of racial segregation. On this occasion he made the celebrated speech "I have a dream", which preached the egalitarian and harmonious coexistence between blacks and whites.
The event took on great proportions and had the adherence of white people, farmers, lawyers, artists and other civil classes, reinforcing the democratic legitimacy of the petitions. In the following years, framing the Civil Rights Act, which ended with several state systems of racial segregation, and the Voting Rights Act, enabled the vote of black people.