《The world of science》PartⅡ PPT课件

外研版高中英语必修三《The world of science》PartⅡ PPT课件，共19页。

《The world of science》PartⅡ PPT课件包括语法精讲、即学即练等内容。

一、基本特征感悟

①Over time I have been changed quite a lot.

②Since the 1970s many new applications have been found for me.

③The important problem has been discussed for nearly two weeks.

④The ink has not been removed from the clothes.

⑤Haven’t your problems been solved?

⑥How many buildings have been built in your school?

二、主要用法精讲

1.结构

Already this year，115 measles cases have been reported in the USA，compared with 189 for all of last year.

今年美国已经报告了115例麻疹病例，而去年全年共189例。

The construction of the bridge has not been finished.桥的建设还没有完成。

Has the date for the next meeting been decided？下次会议的日期已决定了吗？

How long has the battery not been changed？电池多久没有更换了？

2.用法

(1)现在完成时的被动语态同它的主动语态一样，强调过去的动作对现在造成的影响或结果，通常与already，yet，just，never，recently等副词连用。

The machine has already been repaired.机器已经修好了。

(2)表示一个被动的动作或状态开始于过去，持续到现在，并可能持续下去，常与for或since引导的时间状语连用，或用于“How long...？”句型中。

Financial problems of the company have been discussed for nearly two hours.

公司的财务问题已被讨论了近两个小时了。

How long has this film been shown？这部电影已放映多长时间了？

3.注意事项

... ... ...

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