by⁶

by 短语表示过去时间时,最常见的情况是与过去完成时连用。by 短语表示将来时间时,最常见的情况是与将来完成时连用。

1. By the age of 21 he had already begun to notice that it was difficult to move around without falling over. 到21岁时他就已经察觉到，他一走动就难免摔倒。

2. By the end of this month, we shall have carried out the production plan. 到本月底我们将完成生产计划。

3. By 1999 the population will have risen to over 20 million. 到 1999 年人口将超过二千万。

4. We've still got a little food and water and maybe by tomorrow morning the weather will have cleared up. 我们还有一点儿食物和水。也许明天早晨天就会晴了。

5. By the end of July I'll have read all those books. 到7月末我将读完所有这些书。但是，表示时间的 by 短语也可以与一般时态或进行时态连用：

6. I'm always up by eight o'clock. 我总是8点前起床。

7. Can you pay me back by Friday? 你能在周五之前把钱还给我吗？

8. Will you finish it by tomorrow? 你可以不迟于明天把它完成吗？

9. By the time we got to the station, the train ____ for 5 minutes. So we had to give up the trip.

A. had left B. left C. was away D. had been away(北京会考,95-22)

2. By the time I left the school I ____ that course for ten years. A. taught B. have taught C. had taught D. has taught

3. He will have learned English for eight years by the time he ____ from the university next year. A. will graduate B. will have graduated C. graduates D. is to graduate(上海高考,02-23)