Since 1954, when the Supreme Court ruled that segregation

Since 1954, when the Supreme Court ruled that segregation was unconstitutional, the Supreme Courtheard cases in which lawyers debated what constituted segregation.

(A) heard cases in which lawyers debated what constituted segregation
(B) had heard cases in which lawyers debated what constituted segregation
(C) has heard cases in which lawyers debated what constituted segregation
(D) has heard cases in which lawyers debated what has constituted segregation
(E) was hearing cases in which lawyers
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