2.till / until的用法

　　A warning news report from Qatar announces that a group of terrorists will continue to kill Americans wherever they are ________ they leave the Arab world forever.

　　A. even though B. in case

　　C. whenever D. until

　　二、地点状语从句 where

　　三、原因状语从句 because, since, as(因为) , now that, in that

　　四、结果状语从句 so … that... ,such… that…

　　1.After the war, a new school building was put up ___________there had once been a theatre.

　　A. that B. where

　　C. which D. when

　　2.There were some chairs left over ______ everyone had sat down.

　　A.when B. until

　　C. that D. where

　　3.It must have rained last night, _____the ground is wet this morning.

　　A. since B. because

　　C. as D. for

　　Since：既然(双方已知，显而易见)

　　Because：因为(直接原因)

　　As：由于(双方已知)

　　For：因为(表示对结果的“解释”/“推断”)

　　4._______the rain has stopped, let’s continue to work.

　　A. For B. Now that

　　C. That D. Because

　　5._____ you are free tonight, why not drop in and play chess with me?

　　A. For B. Since

　　C. Because D. Even if

　　6.Why not buy a cheaper one, _____ you don’t have enough money?

　　A. since B. because

　　C. for D. though

　　7.It was _____ he was ill that he didn’t go with us.

　　A. since B. for

　　C. as D. because

　　比较：because,since,as和for

　　1) because语势最强，用来说明人所不知的原因,回答why提出的问题，是句子中的重要部分，常放在句末，不能用其它三个替换。逗号可加可不加。

　　You can trust those products because the quality never changes.

　　I haven”t been to the cinema lately,because I am too busy.

　　I didn’t go,because I was afraid.

　　2)当原因是显而易见的或已为人们所知，就用as或 since，since稍正式一些。

　　Since /As the weather is so bad,we have to delay our journey.

　　3) 由because引导的从句如果放在句末，且前面有逗号，则可以用for来代替。但如果不是说明直接原因，而是多种情况加以推断，就只能用for。

　　He is absent today,because / for he is ill.

　　He must be ill,for he is absent today.