not only tom but also bob has been to that island before

来源：学生作业帮编辑：搜狗做题网作业帮分类：英语作业时间：2024/07/15 10:23:56

not only tom but also bob has been to that island before
这句话是对的,可是before为啥这里用在完成时态呢not only tom but also bob was to that island before 实际上题目是这样的not only tom but also bob___(be) to that island before

ago 通常与一般过去时连用,不能与完成时连用；before通常与过去完成时连用.
很显然这里填现在完成时就近原则,bob单三填 has been to（去过某地）
你这句就不对了,原因你懂得.
祝你学习进步
再问： before也与一般过去连用啊，原因我不懂
再答： before与一般过去连用是做的是介词。 I forgot to take the key before going out yesterday（before做介词，动词用ing形式）而这里是副词，所以用现在完成时。这也就是原因啊！
再问：不懂啊，副词，介词什么的，我怎么知道啊，这句话的意思不是之前去了某某地吗，看到你的消息了………………
再答：那好吧从其他角度入手意思是之前去过（have been to去过某地）那个岛，既然是之前去的，那么就是已经完成（做过）的事了，所以就用现在完成时。 before做介词，在句中不能单独使用，所以后面必须跟一些其他的（名词、代词、动名词）连用，而做副词时，后面什么也不跟，做时间状语（和today，tomorrow，next day......一样）。你只需记住before在句末时，一定做的副词，用完成时。
再问：懂了，是不是before表示从前，也就是副词时，用完成时，也就是此时before是单独的时间状语，而before当介词时，是在……以前，后面后跟一些东西，此时用过去，对吧
再答：非常对，恭喜你学懂了

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