◎ 题干
___ countless failures, the scientist finally succeeded in discovering the chemical substance.
[      ]
A. Suffered    
B. Being suffered    
C. To suffer      
D. Having suffered
◎ 答案
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◎ 解析
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◎ 知识点
    根据魔方格专家分析,试题“___ countless failures, the scientist finally succeeded in discovering the chemical substance. [ ]A. SufferedB. Being sufferedC. To sufferD. Having suffered…”主要考查了你对  【现在分词的完成式】  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。