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Little _____ about A-H1N1 so far, so there is no doubt that many people are afraid when talking about the
disease.

A. did scientists know
B. scientists have known
C. have scientists known
D. had scientists known
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科目：高中英語 來源：安徽省模擬題 題型：單選題

Little _____ about A-H1N1 so far, so there is no doubt that many people are afraid when talking about the
disease.
[     ]
A. did scientists know
B. scientists have known
C. have scientists known
D. had scientists known

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