BBC news 2010-04-05 加文本

since是一个用法极活跃的词，现归纳如下：

　　用作介词，意思是“从……以来；自从”，常与完成时连用。

　　I haven't heard from her since last year. 自去年以来我没有收到她的来信。

　　用作副词，意思是“从那时以来”。

　　I saw him last year, but we haven't met since. 我在去年见到过他，从那以后我们就没有见面。

　　用作连词，意思是“从……以来；由于；既然”等。

　　He has been ill since I saw him last. 从上次我见他以来，他一直在生病。

　　Since you have finished the work, let's go to the park. 既然你已把工作做完了，我们去公园吧。

2.Three thousand people have been working around the clock to try to pump out the water in the flooded mine in northern China. Now, their efforts have at least partially paid off.

around the clock昼夜不停,连续一整天;毫不疲倦地,不松劲地

例句：The workers work in three shifts around the clock.
      工人们日夜不停地分三班轮流干活。

pay off使得益; 有报偿

例句：The investor believes that his investment will pay off handsomely soon.
      这个投资者相信他的投资不久会有相当大的收益。

      John studied hard before the examination, and it paid off.He made an A.
      约翰在考试前努力学习, 这没有白费, 他得了个A。

3.President Morales, who wants to redistribute natural resources and land in favor of Bolivia's indigenous people, needs to win in most of the nine states.

in favor of赞成...;支持...;有利于...

例句：All in favor of this proposition will please say“Aye”.
      请所有赞成这项提议的人讲一声“赞成”。

4.But on this occasion, after smashing a hole in the wall at about four in the morning, the robbers set off an alarm.

set off点燃, 爆炸

例句：Be careful that you don't set the fireworks off by mistake.
      当心点, 别弄错了引起那些爆竹爆炸。

      The children are setting fireworks off in the garden.
      孩子们在花园里燃放烟火。