中文谷______scientistshavedonealotofresearchonA(H1N1)flu,ther...
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问题详情：
______ 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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