◎ 题干
Three weeks having gone by, the cause of the accident _____ unknown to the public.      
[     ]
A. remains                      
B. is remaining      
C. has remained                  
D. is remained
◎ 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“Three weeks having gone by, the cause of the accident _____ unknown to the public.[ ]A. remainsB. is remainingC. has remainedD. is remained…”主要考查了你对  【一般现在时】  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。