7.非限制性定語從句

　　非限制性定語從句修飾先行詞或整個主句，起補充說明的作用，如果省略掉，原句句意仍保持完整。非限制性定語從句要用逗號與主句隔開，其引導詞不能用that。非限制性定語從句屬于正式語體。經常考到的非限制性定語從句有以下三種。

　　1) 由which、as引導的非限制性定語從句。which、as代表整個主句。

　　He said that he had never seen her before, which was not true.

　　China is still a developing country, which is known to all of us.

　　2) 由 “介詞+關系代詞”引導的非限制性定語從句。

　　He sent her a letter, in which he said that he was sorry for what he had done to her.

　　He failed to pass the exam, because of which his parents scolded him.

　　4) 由 “數詞、代詞或名詞+of +關系代詞”引導的非限制性定語從句。

　　He had three sons, one of whom was my son’s classmate.

　　There are about twenty students in this course, most of whom are freshmen.

　　They are two different words, the spellings of which are easily confused.

　　Ⅱ 狀語從句

　　1. 狀語從句中以下四種從句考得較多，這里給予簡單介紹。

　　1) 時間狀語從句

　　時間狀語從句主要由以下連詞引導：when, whenever, as, while, since, until, till, before, after, as soon as, once, hardly (scarcely) … when, no sooner … than。

　　I will discuss the matter with you when we meet tomorrow.

　　He didn’t go to sleep until he finished doing his homework.

　　You have changed a lot since we met last time.

　　時間狀語從句還可由某些可充當連詞的名詞(the moment, the instant, every time,等)和副詞(instantly, directly等)引導：

　　I will tell you the news the instant I know.

　　Directly the teacher came in everyone was quiet.

　　Note:

　　① before除了可表示 “在…之前”外，還可用來強調主句所表達的時間、距離很長或花費的力量相比較大，可譯為“…才”。(“not … before” 可用來強調主句所表達的時間、距離很短或花費的力量相比較小，可譯為“…就”)。

　　It was a long time before I got to sleep again.

　　They had not been married a month before they quarreled.

　　② 如果位于when引導的分句之前的主句使用過去進行時、過去完成時或“was/were about to, was/were on the point of”等結構時，when表示突然發生某事，可譯為“正在…突然”或“剛…就”等。這時，不能夠用as或while來代替when。

　　I was walking on the street when I ran into my old friend John.

　　She had just fallen asleep when the telephone rang.

　　We were about to leave when it began to rain.

　　2) 條件狀語從句

　　條件狀語從句主要由以下連詞引導：if, unless, providing/provided (that), suppose/supposing (that), on condition (that), as/so long as, in case等。

　　So long as you work hard, you will surely achieve good results in examinations.

　　I shall return next Thursday unless something unexpected happens.

　　I will go provided that you go with me.

　　Please give this letter to John in case he comes.

　　3) 讓步狀語從句

　　讓步狀語從句主要由以下連詞引導：though, although, even if, even though, whatever, however, whoever, wherever, no matter how/ what/ where/ when等。以下介紹幾種較特殊的讓步狀語從句。

　　(1) while引導的讓步狀語從句多放在句首，while相當于although，表示“盡管”，“雖然”。

　　While I admit I did it, I didn’t intend to.

　　While I understand what you say, I can’t agree with you.

　　(2) 短語“even now/then/so”相當于“though it is/was true”，表示“盡管如此”，“盡管這樣”。

　　The fire was out, but even so, the smell of smoke was strong.

　　I’ve tried my best, but even now/then she is not satisfied.

　　(3) as引導的讓步狀語從句要倒裝。

　　Child as he was, he could speak four languages.

　　Hard as she tried, she failed to get the job.