"Once" is used in an adverb clause to show time relationship. The meaning of "once" is similar to "when."
"Because of "is a preposition that is followed by a noun object; it is used to show a reason.
it should be 'makes for'
it should be 'used'
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.
This question is based on the correct word order. Only (B) has the right order.
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TOEFL Practice Test #9