◎ 题干
The highway through the rain forest was completed in 1990, _____ some animal species have died off.
A. by when
B. since then
C. since when
D. by which time
◎ 答案
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“The highway through the rain forest was completed in 1990, _____ some animal species have died off. [ ]A. by when B. since then C. since when D. by which ti…”主要考查了你对  【关系副词】【介词和介词短语】【非限制性定语从句】  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。