it should be 'used'
"Once" is used in an adverb clause to show time relationship. The meaning of "once" is similar to "when."
it should be 'makes for'
This question is based on the correct word order. Only (B) has the right order.
The noun "educator" is needed to modify the adjective " a leading African-American."
A time preposition is needed here. Although all the choices deal with time, only "during" is the correct answer; it emphasizes a point in time.
"Because of "is a preposition that is followed by a noun object; it is used to show a reason.
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TOEFL Practice Test #9