The correct option is option B ("A legal issue shared by a number of cases").
The Brown v. Board of Education case was taken up by the Supreme Court as a combination of five different cases sharing the same legal issue (Briggs v. Elliott (filed in South Carolina), Davis v. County School Board of Prince Edward County (filed in Virginia), Gebhart v. Belton (filed in Delaware), and Bolling v. Sharpe (filed in Washington, D.C.).
The argument was that State laws separating black and white students in different public schools, were inflicting a violation of the Equal Protection Clause in the Fourteenth Amendment of the U.S. Constitution. Racial segregation imposed by law, was prompting inequality between public educational facilities. The Supreme Court ended up deciding that this practice was in fact unconstitutional.
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