4、一些重要的时间状语

1）、during the last fifty years最近50年间 （注意last 前面的the）

E：The change that have taken 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.

2）、by:不迟于，在......之前，到......为止

表示动作在某一时刻之前完成，常用于完成时句子。

E1、By the time the doctor arrived the patient had died.（过去完成时）

E2、By 2005 the population will have risen to over 15 billion.（将来完成时）

3）、till/until 直到......

注意和BY的区别，它们表示"某动作完成的终止点"。

E: She finished her experiment by 11o'clock.

She did her experiment till/until 11 o'colck.

4)、so far 到现在为止

so far this morning 今天上午到现在为止

5、练习：

1)、By the time you arrive in London,we_____(stay)in Europe for two weeks.

2)、The first two factors must be equal for all who are being compared,if any comparison in terms of intelligence____(make)

3)、While you were in London that year,the London Bridge_____(repair).

4)、John is't a diligent student,for it is the third time he____(be)late,isn't it?

5)、John always works in his lab and makes a lot of experiments,He___(make)experiments all afternoon and____(not finish)yet.

6)、It___(be)very cold lately,but it's beginning to get a bit warmer.