非限制性定语从句指代整体保持主句的完整性
弄清as 和which 引导的非限制性定语从句指代整体时的区别
1. 位置上的区别：as 引导的非限制性定语从句的位置比较灵活，可以放在主句前，也可以放在主句后，还可插在主句的中间；而which 引导的非限制性定语从句只能放在主句之后。例如：
As is known to us all, the earth turns around the sun.
The earth, as is known to us all, turns around the sun.
The earth turns around the sun, as is known to us all.
The earth turns around the sun, which our parents once told us when we were very young.
2. 词义与联系上的区别：as 引导的非限制性定语从句与主句之间有着较为密切的上下文联系，as 本身含有“正如”之意；而which 引导的非限制性定语从句与主句之间在逻辑意义上近似并列句，which 本身表示“这”或“这一点”之意。例如：
Light travels faster than sound, as we all know.
Jack came late for school, which made his teacher angry.
注意定语从句的主谓一致性关系代词在定语从句中作主语时，从句的谓语必须与先行词保持人称和数的一致。例如：
Tom is one of the boys who are from the USA.
Tom is the only one of the boys who is from the USA.
保持主句的完整性并避免从句成分的重叠
1. 在定语从句中，不管出现任何情况，主句的结构必须完整，即主句必须有主语和谓语，缺一不可，否则，整个主从复合句就无法成立。试比较：
(1)Is this factory _______ we visited last week?
(2)Is this the factory _______ we visited last week?
A. which B. where C. what D. the one
分析：
第一题缺少表语，只有填D项才能保持主句的完整性，而其他的选项均为干扰项。
第二题主句本身完整，应填的关系代词在从句中作visited 的宾语，故应选A项。
2. 从定语从句中，关系代词或关系副词已经代替先行词独立地或与相应的介词一起在定语从句中充当了一定的成分，因此在定语从句中就不能再出现与关系代(副)词重叠的成分。例如：
错句：Is this the train that they took it last Sunday?
分析：该题中that 已经代替先行词the train 在定语从句中充当及物动词took 的宾语，故重叠出现的宾语it必须删去。
1. — Sorry to have interrupted you. Please go on.
— Where was I ?
— You _____ you didn’t like your father’s job.
A. had said B. said C. were saying D. had been saying
2. I arrived late; I _____ the road to be so iey.
A. wouldn’t expect B. haven’t expected C. hadn’t expected D. wasn’t expecting
3. I ______ while reading the English textbook. Luckily, my roommate woke me up in time !
A. had fallen asleep B. have fallen asleep C. fell asleep D. fall asleep
4. Let’s keep to the point or we ______ any decisions.
A. will never reach B. have never reached C. never reach D. never reached
5. My mind wasn’t on what he was saying, so I’m afraid I _____ half of it.
A. was missing B. had missed C. will miss D. missed
答案与解析
1、C 语境中暗含着一个时间信息：当我打断你说话的时候。
2、C arrive是关键信息：(我在出发之前)没有预料到路会这么滑。这里谈论的显然是过去(started)的过去(had expected).
3、C根据woke(wake 的过去式)可以判断，这里谈论的与“现在”无关，因此可以排除B和D两项。I是在读书期间睡着的(while reading),而不是在之前睡着的，所以A项也是不恰当的。
4、A 句意：请不要偏离话题，不然的话，我们就不会取胜得决定。祈使句与and 或or 连用是常见的说法，又如：Turn left and you will find the bookstore.向左转，你就会找到那个书店里。Listen to me or you will never succeed.听我的话，否则，你不会成功的。同时在谈到will do和be going to do 表示将来的区别时，will表意愿和既时的将来，而后者表示计划的或有迹象的将来。例如：
Give him the big apple or he oil not allow us to go with him.
—Why didn’t you come to my birthday party?
—I was going to ,but my wife returned.
5、D 句意：(当时)我并没有注意他说的话，所以(现在)我觉得他讲的话一半我没有听到。题干句中透圳出时间信息的三个地方：wasn’t ,was saying和I’m afraid是做出选择的重要依据。
