______scientistshavedonealotofresearchonA(H1N1)flu,ther...

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问题详情:

______scientistshavedonealotofresearchonA(H1N1)flu,ther...

______ scientists have done a lot of research on A (H1N1) flu, there are still some cases for further study.

A. As   B. Once   C. If     D. Although

【回答】

D

知识点:连词

题型:选择题

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