5、although和though引導(dǎo)讓步狀語從句往往用法一樣，但注意以下區(qū)別：①although用于各種文體，而though則多用于非正式的口語或書面語中。注意由although, though引導(dǎo)的從句后，主句不能用but，但可用副詞yet, still。例如：Although/ Though it rained all the morning, they still went on working.(或yet they went on working)②though常與even連用，even though表示強(qiáng)調(diào)，意為“即使”，但不能說even although，例如：Even though I didn’t understand a word, I dept smiling. ③though可用作副詞，意為“然而”，常用逗號與句子分開。although則不能這樣使用，它只作連詞。例如：It was a quiet party, I had a good time, though.

4、because, since, as引導(dǎo)原因狀語時(shí)注意使用上的區(qū)別：①如果原因構(gòu)成句子的最主要部分,一般用because ,因此because引導(dǎo)的從句往往放在句末。用why提問的句子，一定用because回答。例如：He had to stay at home yesterday because he was ill.；②如原因已為人們所知，或不如句子的其他部分重要，就用as，或 since。since比as更正式些。as和since引導(dǎo)的從句一般放在句子的開頭。例如：As you are tired, you had better rest./ Since everyone is here, now let’s begin.

3、till, until作為介詞式從屬連詞引導(dǎo)時(shí)間狀語短語或狀語從句，用于否定句時(shí)，結(jié)構(gòu)為not …until (till)，主句謂語動(dòng)詞延續(xù)與非延續(xù)皆可，意為“直到…才…”。用于肯定句時(shí)，只與延續(xù)性動(dòng)詞連用，表示“到…為止”。例如：They played volleyball until (till) it got dark./ They didn’t talk(延續(xù)性動(dòng)詞)until (till) the interpreter(譯員)came./ He didn’t go to bed(非延續(xù)性動(dòng)詞)until (till) the his father came back.；until可以放在句首，till則不行，例如：Until the last minute of the match we kept on playing./ Not until he finished his work did he go home.(倒裝)；till, until只用于時(shí)間，以下句子是錯(cuò)誤的：We walked till the edge of the forest.(要用as far as或to)。

2、before作連詞一般表示時(shí)間，意為“在…之前”，但有些句子中這樣譯就顯得別扭。試看以下句子的翻譯：He almost knocked me down before he saw me.他幾乎把我撞倒才看見我；Before I could get in a word he had measured me.我還沒來得及插話，他已經(jīng)給我量好了尺寸。

1、當(dāng)while, when, as引導(dǎo)時(shí)間狀語從句時(shí)的區(qū)別：①while引導(dǎo)的狀語從句中動(dòng)詞必須是持續(xù)性。謂語動(dòng)詞多為進(jìn)行時(shí)，或狀態(tài)動(dòng)詞的一般時(shí)。while 的這些用法可用when代替，等于 “at the time that”, “during the time that”。例如：Please keep quiet while (when) others are studying；② when除可指一段時(shí)間外，還可用來指一點(diǎn)時(shí)間，等于 “at the time”，也就是說when引出的時(shí)間狀語從句中的謂語動(dòng)詞可以是終止性的，也可以延續(xù)性的。因此主句和從句的謂語可以是一般時(shí)，進(jìn)行時(shí)，或完成時(shí)。例如：When I went into the lab, the teacher was doing an experiment.(when不能換成while)He often makes mistakes when he is speaking English.(when可換成while)③as常可與when，while通用，但強(qiáng)調(diào)“一邊、一邊”。例如：As (when, while) I was walking down the street, I noticed a police car in front of number 37. ④when引導(dǎo)的狀語從句中的主語與主句主語一致，主、謂是“主語+系動(dòng)詞”結(jié)構(gòu)時(shí)，這時(shí)主語和系動(dòng)詞可以省略。例如：When (he was) young, he worked for a rich man./ She’ll be here to give you help when (if it is) necessary. ⑤when有時(shí)代替if，引導(dǎo)條件句，意為“如果”、“假如”，例如：I’ll come when (if) I’m free.

50. He is one of the old scientists who ______nothing about his personal income and fame .

　 A. cares　 　　　　　　　 B. care　 　　　　　　　　　　 C. is caring　 　　　 　　　 D. are caring

49. Nobody except Bill and Johnny ______entered the second round of the interview.

A. have　 　　　　　　　　 B. has　 　　　　　　　　　　 C. have been　 　　　　　　 D. has been

48. Every hour and every minute ______ important.

　 A. are　　 　　　　　　　　　　 B. were　　 　　　　　　　　 C. is　 　　　　　　　　　　　 D. will

47.The pilot as well as four of the passengers ______death .

　 A. has escaped　　 　 B. have escaped　 　　　　　　　 C. has been escaped　 　 D. have been escaped

46. They each ______ a new dictionary.

　 A. has　 　　　　　　　　 B. have　　 　　　　　　　　　 C. is　　 　　　　　　　　　　　 D. are