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The lack of complete historical records from the mid-to-late 1800's have made some Black inventions difficult to trace to their originators.
(A)have made some Black inventions difficult to trace to their originators (B)have made for difficulties in tracing some inventions by Black to their originators (C)have made it difficult to trace some inventions by Black to their originator (D)has made it difficult to trace some inventions to their Black originators (E)has made it difficult in tracing some Black inventions to their originators
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发表于 2009-4-3 11:12:00
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