三、注意与完成时连用的句型和时间状语

　　（1）by/between/up to/till+过去时间、since、by the time/when+表示过去发生情况的从句，主句用过去完成时。如：

　　We had just had our breakfast when an old man came to the door.

　　Between 1897 and 1919 at least 29 motion pictures in which artificial beings were portrayed had been produced.

　　（表示1919年时已发生的情况）

　　（2）by+将来时间、by the time/when+谓语动词是一般现在时的从句，主句用将来完成时。如：

　　By the time you arrive in London, we will have stayed in Europe for two weeks.

　　I hope her health will have improved greatly by the time we come back next year.

　　（3）by now、since+过去时间、in/during/for/over/the past/last few（或具体数字）years/days/months，主句用现在完成时，但在it is+具体时间since/before这一句型中，主句更多的时候不用完成时。如：

　　The changes that howe taken place place in air travel during the last sixty years would have seemed completely impossible to even the most brilliant scientists at the turn of the 19th century.

　　It is four years since John left school.

　　（4）在It is the+序数词/形容词最高级+that的定语从句中，谓语动词常用现在完成时。如：

　　It isn't the first time that I have found myself in an embarrassing situation.

　　（5）在no sooner…than…, hardly/scarcely…when/before…句型中，主句常用过去完成时。

　　（6）其他与完成时连用的时间状语：all this while，all this year，for some time，so far，already，before，just，long，yet等。

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