◎ 题干
It is clear that no use can be made ______radium _____ we don’t know clearly the characteristics of it.
[     ]
A. from; if    
B. of; unless  
C. from; unless  
D. of; if
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“It is clear that no use can be made ______radium _____ we don’t know clearly the characteristics of it. [ ]A. from; ifB. of; unless C. from; unless D. o…”主要考查了你对  【介词和介词短语】【从属连词】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。