By the time he was twelve, Edison had began to make a living by himself.

这个句子中的by，是直到还是到的意思，还有had能不能换成have?谢谢啦

推荐答案 2010-02-27

By是到的意思
主句必须用完成时
Edison是爱迪生啊，早就不在了，所以用过去时

[表示时间关系]在…期间，在(白天、夜晚)的时候：例句: to travel by night
在夜间旅行to work by day
在白天工作在固定的时间内：例句: to work by the hour
按钟点工作不迟于；到…时(为止)，到(某时)之前：例句: Be back by ten o'clock.
10点以前回来。We usually finish work by six o'clock.
我们通常在6点钟之前完成工作。在…环境下，以…为伴：例句: Jack and Mary walked by moonlight.
杰克和玛丽在月光下散步。

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其他回答

第1个回答 2010-02-27

这句是典型的用过去完成时的句子。
主要是看By后面的时间点是过去的还是将来的
即，如果By后面接的是表将来的，则用将来完成时：如果后面接的是表过去的，则用过去完成时，所以不能换成have.
记住那个规则，这种句子就很好做了。

第2个回答 2010-02-27

应该是到的意思,不能用have,因为后半句是完成时前面用was 所以是过去完成时,用had

第3个回答 2010-02-27

在爱迪生十二岁之前，他就已经自己养活自己了。
by是“在...之前”的意思。By the time he was twelve是过去完成时的标志，所以had不能换成have。

第4个回答 2010-02-27

by意思是“不晚于”，“在。。。之前”

12岁之前就开始自己谋生，所以是过去的过去，用过去完成式had begun

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