31.(2008浙江) Don’t promise anything __________ you are one hundred percent sure.
A. whether B. after C. how D. unless
答案：D
解析：句意“除非你有百分百的把握，否則不要作出任何承諾”，unless表示“除非，如果不”，相當于if not，如果把后半句改為if you are not one hundred percent sure，就比較容易理解了。

32.(2008江西) Animals suffered at the hands of man __________ they were destroyed by people to make way for agricultural and to provide food for more people.
A. in which B. for which C. so that D. in that
答案：D
解析：句意“動物遭受來自人類的滅頂之災，因為人們摧毀它們是為了開墾更多的耕地來滿足更多的人對食物的需求”。at the hands of“出自……之手”，in that“因為”。

33.(2008四川) In some places women are expected to earn money __________ men stay at home and raise their children.
A. but B. while C. because D. though
答案：B
解析：句意“在一些地方人們期望女人去掙錢，而讓男人在家撫養(yǎng)孩子”，此處while的意思是“而”，表示對比。but不強調(diào)對比，因此不恰當。

34.(2008全國II) A small car is big enough for a family of three __________ you need more space for baggage.
A. once B. because C. if D. unless
答案：D
解析：前面主句意思是：小汽車足以供一個三口之家使用。后面的從句表示你需要更多的空間裝行李。主從句的關系是一種條件關系，意思是：如果你不需要更多的空間裝行李的話，小汽車足以供一個三口之家使用。故選D。

35.(2007北京) Leave your key with a neighbor __________ you lock yourself out one day.
A. ever since B. even if C. soon after D. in case
答案：D
解析：in case意為“以防萬一”。根據(jù)所提供的情景“Leave your key with a neighbor”可判斷出表示“把你的鑰匙留給你的鄰居一把，以防萬一有一天你被鎖在外邊”，故選D。

36.(2007安徽) The field research will take Joan and Paul about five months, it will be a long time __________ we meet them again.
A. after B. before C. since D. when
答案：B
解析：before意為“在……之前”。根據(jù)所提供的情景“The field research will take Joan and Paul about five months”可判斷出表示“要很長時間我們才能再見面”。

37.(2007福建) You will be successful in the interview __________ you have confidence.
A. before B. once C. until D. though
答案：B
解析：once用作連詞時意為“一旦……就……”。句意為“一旦你有信心，你在面試中就會成功”。

38.(2007湖南) Most birds find it safe to sleep in the trees, but __________ they have eggs or young chicks, they don’t use a nest.
A. why B. how C. unless D. where
答案：C
解析：unless引導讓步狀語從句，意為“如果不”。根據(jù)they have eggs or young chicks和they don’t use a nest可判斷出前句是后句的條件，表示“如果它們不下蛋或沒有小雞，它們就不用窩”。

39.(2007江西) He was told that it would be at least three more months __________ he could recover and return to work.
A. when B. before C. since D. that
答案：B
解析：before引導時間狀語從句，意為“在……之前”，表示“他康復后重返共組哦方位至少還要三個月的時間”。

40.(2007天津) It is difficult for us to learn a lesson in life __________ we’ve actually had that lesson.
A. until B. after C. since D. when
答案：A
解析：until引導時間狀語從句，意為“直到……”，表示主句的動作一直延續(xù)到until從句中的動作發(fā)生前。

?