In his arguments in brown v. board of education the lawyer for oliver and linda brown claimed that separate but equal public schools were

 NOT TRULY EQUAL

Historical context:

Brown v. The Board of Education (1954) overturned an older Supreme Court decision in Plessy v. Ferguson (1896), which had said that segregation laws were acceptable as long as equal facilities were available.  Brown v. The Board of Education asserted that separate educational facilities are inherently unequal and therefore the "separate but equal" policy was unconstitutional.  The decision in Brown v. the Board of Education mandated an end to segregation in education.

the answer here would be

b. ensure mutual protection from communism.

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