關(guān)系代詞所代替的先行詞是人或物的名詞或代詞，并在句中充當(dāng)主語、賓語、定語等成分。關(guān)系代詞在定語從句中作主語時，從句謂語動詞的人稱和數(shù)要和先行詞保持一致。
1）who, whom, that 這些詞代替的先行詞是人的名詞或代詞，在從句中所起作用如下： Is he the man who/that wants to see you? 他就是你想見的人嗎？（who/that在從句中作主語） He is the man whom/ that I saw yesterday. 他就是我昨天見的那個人。（whom/that在從句中作賓語）
2) whose 用來指人或物，(只用作定語, 若指物，它還可以同of which互換), 例如： They rushed over to help the man whose car had broken down. 那人車壞了，大家都跑過去幫忙。 Please pass me the book whose (of which) cover is green. 請遞給我那本綠皮的書。
3) which, that 它們所代替的先行詞是事物的名詞或代詞，在從句中可作主語、賓語等，例如： A prosperity which / that had never been seen before appears in the countryside. 農(nóng)村出現(xiàn)了前所未有的繁榮。（which / that在句中作賓語） The package (which / that) you are carrying is about to come unwrapped. 你拿的包快散了。(which / that在句中作賓語)
4) 關(guān)系副詞可代替的先行詞是時間、地點或理由的名詞，在從句中作狀語。 1）when, where, why關(guān)系副詞when, where, why的含義相當(dāng)于"介詞+ which"結(jié)構(gòu)，因此常常和"介詞+ which"結(jié)構(gòu)交替使用，例如： There are occasions when (on which) one must yield. 任何人都有不得不屈服的時候。 Beijing is the place where (in which) I was born. 北京是我的出生地。 Is this the reason why (for which) he refused our offer? 這就是他拒絕我們幫助他的理由嗎？
5）that代替關(guān)系副詞 that可以用于表示時間、地點、方式、理由的名詞后取代when, where, why和"介詞+ which"引導(dǎo)的定語從句，在口語中that常被省略，例如： His father died the year (that / when / in which) he was born. 他父親在他出生那年逝世了。 He is unlikely to find the place (that / where / in which) he lived forty years ago. 他不大可能找到他四十年前居住過的地方。
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注意事項
What只能引導(dǎo)名詞性從 句， 用作連接代詞，作從句的具體成分，且不能省略。 I think (that) you will like the stamps. What we need is more practice.
