问题描述：
在线等!求大神分析这句下语法...there has been a need for sth
there has been a need for sth 不懂为什么是there has been?真是什么时态呢,.能详细些么 谢谢了!
there has been a need for sth 不懂为什么是there has been?真是什么时态呢,.能详细些么 谢谢了!
问题解答：
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