同学你好，该知识点来自沪江网校《英语零基础直达CATTI笔译三级【随到随学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学好
The trees had been there for centuries. 正确
The trees had been there since centuries. 错误（since后面只能跟时间点不能跟时间段，可以改成The trees had been there since last century）
The trees had been there before centuries. 错误（before后加时间点，比如before 2008）
The trees had been there centuries long. 错误 （long一般接具体的数字，比如13 centuries long）
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