The correct answer is D.
Brown v. Board of Education was the landmark decision enacted by the US Supreme Court in 1954, that outlawed segregated education in the US.
The case was about the constitutionality of the "separate but equal" lemma that was accepted in the former decision enacted by the US Supreme Court in 1896 in the Plessy v. Ferguson case. Such decision allowed the proliferation of segregated schools under the belief that, if facilities were equal in quality, such education system was not violating the equality of rights provision that had been guaranteed for all US citizens by the Reconstruction Amendments to the US Constitution.
Brown v. Board of Education overturned the abovementioned previous Supreme Court decision and declared segregation unconstitutional, giving a deadline to all schools nationwide to abolish such practice. The decision was written by justice Earl Warren.