BBC news 2009-08-24 加文本

1.The wooded hillsides on the outskirts of the capital acted as its lungs and air conditioning units, providing much needed oxygen and cooler air.

act as担任,扮演,充当,起…作用

例句：Then you have to act as a dishwasher yourself.
       那么就由你来充当洗碗机吧。

       Who will act as mediator in the dispute.
        谁在争端中充当调解人?

2.The two-week offensive by the Yemeni government intended to crush a long-running rebellion in the north of the country is continuing with air strikes on rebel positions.

intend to打算(做)..., 想要(做)...

例句：I intend to contest the judge's decision in another court.
      我打算到另一个法庭去对法官的判决进行抗辩。

3.The Yemeni army launched its offensive in the north two weeks ago with the aim of crushing the rebels once and for all.

with the aim of以…为目的，相当于In order to

例句：He often strikes a pose in order to intimidate people.
       他常装腔作势借以吓人。

once and for all一劳永逸地,永远,彻底地

例句：I'm warning you once and for all.
       我给你最后一次警告。

4.The Egyptian authorities began arresting members of the alleged Hezbollah cell last year, ratcheting up tensions with the Lebanese group and its state backer Iran.

ratchet up增加；渐进

例句：Prime Minister Blair told the House of Commons that it is now time to ratchet up the international and diplomatic  pressure on Iran to secure the sailors' release.
        布莱尔首相告诉下院，现在还不是时候向伊朗增加国际和外交压力，使其释放水手。