一、in case引導的狀語從句
根據語境的不同，in case既可表示“如果”“萬一”，引導條件狀語從句;也可表示“以防(萬一)”，引導目的狀語從句。下面兩道真題均選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. (重慶卷)
A. if B. unless C. in case D. so that
【解析】兩道題都選in case，均表示“以防萬一”。
二、before引導的狀語從句
尤其要注意“it+be+一段時間+before…”這一句型。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】兩道題均before。第1題涉及的句式為：It will be a long time before…，意思是“要過很久才會……”;第2題涉及的句式為：it was some time before…，意思是“在……之前過了一段時間”，通常可轉譯為“要過一段時間才會……”。
三、while引導的狀語從句
尤其要注意while表示“盡管”“雖然”時的用法(此時它引導的不是時間狀語從句，而是讓步狀語從句——此用法許多同學并不熟悉，值得特別注意!)。如：
______ I really don’t like art I find his work impressive. (山東卷)
A. As B. Since C. If D. While
【解析】答案選D。while在此表示“盡管”“雖然”，又如：While the work was difficult it was interesting. 盡管工作有難度，但很有趣。/While I understand what you say I can’t agree with you. 雖然我理解你的意思，但我還是不同意。
另外，while表示對比的用法也值得注意(此時它表示“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引導的狀語從句
對于when的用法，同學們最熟悉的是表示“當……的時候”。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】答案選B。將四個選項逐一填入空格處，只有填when時，意思最通順。句意為：當你昨天在布萊克先生辦公室時我就帶給你了。
但是when還有一個用法，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
還有一點也需注意，就是when表示“這時(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. (遼寧卷)
A. why B. where C. when D. while
