○3 只能用which的情況：
a． 關系代詞前有介詞。 This is the house in which we lived last year .
b． 先行詞本身是that 。 The clock is that which I bought yesterday .
c． 非限制性定語從句。 His English , which used to be very poor, is now excellent .
○4 定語從句在句中作定語，所以在使用時，相當于現在分詞短語，過去分詞短語，動詞不定式短語，介詞短語作后置定語的句子。
a．I bought a book that was written by Lu Xun . = I bought a book written by Lu Xun .
b．Tell the children who are playing basketball not to do that . = Tell the children playing basketball not to do that .
c．The house that stands at the corner was built in 1987 . = The house standing at the corner was built in 1987 .
d．We have nothing that we should fear . = We have nothing to fear .
e．The book that is on the table is expensive . = The book on the table is expensive .
○5 引導詞when, where和why可用相應的表示時間（in, on, at, during等）、地點（in, on, at等）和原因（for）的介詞＋which 表達為介賓結構。
a．I still remember the day when I met her for the first time . ---- I still remember the day on which I met her for the first time .
b．That is the place where I went when I was a child . ----- That is the place to which I went when I was a child .
c．May I know the reason why you are late ? ----- May I know the reason for which you are late ?
○6 在定語從句中，不能再出現指示先行詞的指示代詞。
I just can't find the book which/that she lent it to me .（×）---- I just can't find the book which/that she lent to me .（√）
○7 注意下面的變化：
a． This is the house(不作lived的賓語) where we lived last year .
This is the house(作lived in的賓語) which/that we lived in last year .
b． This is the day (不作left的賓語)when we left for Shenzhen .
This is the day (作spent的賓語)which/that we spent in Shenzhen .
○8 限制性定語從句和非限制性定語從句的區別：
a． 限制性定語從句：是句中不可缺少的組成部分，沒有從句，先行詞意思不明確，主句也不完整，從句主句不用逗號分開。
b． 非限制性定語從句：是主句先行詞的補充說明，沒有從句并不影響主句意思的明確或完整，這種定語從句一般用逗號和主句分開，在非限制性定語從句中，一般不用that。
◎ Last Sunday they reached Dalian, where a meeting was to be held .
◎ She has two brothers, who are both doctors .
Ⅲ There be 句型
1． 英語"There + be + (not)"結構表示"有（沒有）某人或某物"時，there 是無詞義的引導詞，be是謂語動詞，它后面的名詞是主語，兩者再數上必須一致。句末往往有表示地點或時間的狀語。
2． 肯定句：There +(助動詞或情態動詞)＋be 主語＋地點（時間）狀語。
There is a pen on the table . / There will be a football match tomorrow .
3． 否定句：There + be(助動詞或情態動詞)＋not（any）(或＋no)+ 主語…。
There are not fairies in the world . / There wasn't a underground in Shanghai before ./ There won't be a football match tomorrow .
4． 一般疑問句：Be + there +(any) +主語… ？ / 助動詞或情態動詞 ＋ there +be +(any) + 主語… ？
Is there anything I can do for you ? / Will there be cloud tomorrow ?
5． 特殊疑問句：疑問詞（＋名詞）＋be ＋there + 狀語 ？
How many weeks are there in a year ? / What is there on the desk ? / Where will there be a football match tomorrow ?
6． 如果there +be 之后是并列主語，應根據離be 最近的名詞來選擇be的形式。
There is a apple and two pears on the table . / There are two pears and a apple on the table .
7． 含有引導詞there 的句子用seem to be , happen to be , used to be 或live 等作謂語的結構。
There happened to be an old friend of mine in the shop . / There used to be a temple here