一、in case引导的状语从句
根据语境的不同，in case既可表示“如果”“万一”，引导条件状语从句;也可表示“以防(万一)”，引导目的状语从句。下面两道真题均选in case：
1. Leave your key with a neighbor ______ you lock yourself out one day. (北京卷)
A. ever since B. even if C. soon after D. in case
2. My parents live in a small village. They always keep candles in the house ______ there is a power cut. (重庆卷)
A. if B. unless C. in case D. so that
【解析】两道题都选in case，均表示“以防万一”。
二、before引导的状语从句
尤其要注意“it+be+一段时间+before…”这一句型。如：
1. The field research will take Joan and Paul about five months; it will be a long time ______ we meet them again. (安徽卷)
A. after B. before C. since D. when
2. He was told that it would be at least three more months ______ he could recover and return to work. (江西卷)
A. when B. before C. since D. that
【解析】两道题均before。第1题涉及的句式为：It will be a long time before…，意思是“要过很久才会……”;第2题涉及的句式为：it was some time before…，意思是“在……之前过了一段时间”，通常可转译为“要过一段时间才会……”。
三、while引导的状语从句
尤其要注意while表示“尽管”“虽然”时的用法(此时它引导的不是时间状语从句，而是让步状语从句——此用法许多同学并不熟悉，值得特别注意!)。如：
______ I really don’t like art, I find his work impressive. (山东卷)
A. As B. Since C. If D. While
【解析】答案选D。while在此表示“尽管”“虽然”，又如：While the work was difficult, it was interesting. 尽管工作有难度，但很有趣。/ While I understand what you say, I can’t agree with you. 虽然我理解你的意思，但我还是不同意。
另外，while表示对比的用法也值得注意(此时它表示“而”)。如：
The cost of living in Glasgow is among the lowest in Britain, ______ the quality of life is probably one of the highest. (天津卷)
A. since B. when C. as D. while
四、when引导的状语从句
对于when的用法，同学们最熟悉的是表示“当……的时候”。如：
—Where’s that report?
—I brought it to you ______ you were in Mr. Black’s office yesterday. (北京卷)
A. if B. when C. because D. before
【解析】答案选B。将四个选项逐一填入空格处，只有填when时，意思最通顺。句意为：当你昨天在布莱克先生办公室时我就带给你了。
但是when还有一个用法，就是表示“既然”。如：
Why do you want a new job ___D___ you’ve got such a good one already?
A. that B. where C. which D. when
还有一点也需注意，就是when表示“这时(突然)”的用法。如：
1. I had just stepped out of the bathroom and was busily drying myself with a towel ___B___ I heard the steps. (湖南卷)
A. while B. when C. since D. after
2. He was about halfway through his meal ___C___ a familiar voice came to his ears. (辽宁卷)
A. why B. where C. when D. while
五、unless引导的状语从句
unless的意思是“如果不……”“除非”，对于涉及unless的考题，一般只要能读懂句意，弄清语境，一般不会有问题。如：
1. Most birds find it safe to sleep in the trees, but ______ they have eggs or young chicks, they don’t use a nest. (湖南卷)
A. why B. how C. unless D. where
2. I won’t call you, ______ something unexpected happens. (全国I)
A. unless B. whether C. because D. while
【解析】两道题都选unless，均表示“除非”。
六、until引导的状语从句
until的意思是“直到……时”“在……之前”，对于涉及until的考题，一般只要能读懂句意，弄清语境，一般不会有问题。如：
It is difficult for us to learn a lesson in life ___A___ we’ve actually had that lesson. (天津卷)
A. until B. after C. since D. when
另外，还要注意not…until…这一句式(直到……才)。如：
“You can’t have this football back ___D___ you promise not to kick it at my cat again,” the old man said firmly. (广东卷)
A. because B. since C. when D. until
七、once引导的状语从句
once的意思是“一旦”，对于涉及once的考题，一般只要能读懂句意，弄清语境，一般不会有问题。如：
1. You will be successful in the interview ______ you have confidence. (福建卷)
A. before B. once C. until D. though
2. ______ environmental damage is done, it takes many years for the ecosystem (生态系统) to recover. (江苏卷)
A. Even if B. If only C. While D. Once
【解析】两道题都选once，均表示“一旦”。
八、where引导的状语从句
where可以用于引导地点状语从句，其意为“在……的地方”，此用法许多同学都不是熟悉，但高考经常考查，应引起特别注意。如：
1. If you are traveling ______ the customs are really foreign to your own, please do as the Romans do. (天津卷)
A. in which B. what C. when D. where
2. —Mom, what did your doctor say?
—He advised me to live ______ the air is fresher. (四川卷)
A. in where B. in which C. the place where D. where
【解析】两道题都选where，均表示“在……的地方”。
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