问题：[单选,材料题题]

[单选,材料题] Who are the first to make the success of sit-in become true?

回答下面的题目
    American Blacks experienced a revolution after 1945, a revolution in expectations．  Following World War Ⅱ , the steady movement toward first-class citizenship for Black people quickened, with significant actions taking place in courts of law, in voting booths, in restaurants and in the streets of the nation．
    A decade of intense civil rights activity was launched in 1954 when the United States Supreme Court declared segregated schools to be unconstitutional．  In 1955, Dr．  Martin Luther King, Jr． , effectively organized the Blacks of Atlanta, Georgia, in a bus boycott． The boycott lasted two years, and when it was over, Blacks no longer were degraded by being forced to sit or stand in the rear of buses．
    In 1960, a group of Black college students decided that they, as well as white persons, had the right to eat at a lunch counter in Greensboro, North Carolina．  This sit-in sparked an aggressive national movement and, in the next few years, thousands of young men and women--Black and White, North and South--overturned local laws and customs that had maintained segregation． Sit-ins, pray-ins, freedom rides, freedom marches and demonstrations to open all schools to Black children took place across the nation．

Several important actions took place to change the status of black people

A . Black college students and whites．
B . First-class citizens．
C . The Blacks of Atlanta．
D . Young men and women in Greensboro．