Thescientistsare________aresear

发布时间：2020-07-28 13:10:09

The scientists are ________ a research ________ the cause of heart diseases.A.carried out; onB.carrying out; intoC.performing; inD.performed; of

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B解析导解：这里的习惯搭配为perform/carry out a research on/ into sth.
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