(一)定語從句
1.定語從句的特征
定語從句分為限定性定語從句和非限定性定語從句。限定性定語從句與主句關(guān)系緊密，為句中不可缺少的成分，如去掉，則主句意思不完整或不明確。非限定性定語從句與主句關(guān)系松散，如去掉，主句內(nèi)容仍完整。在書面語中，非限定性定語從句一般用逗號(hào)與主句隔開。
引導(dǎo)定語從句的關(guān)聯(lián)詞包括：
(1)關(guān)系代詞：that，which，whose，who, whom，as。
(2)關(guān)系副詞：when，where，why。
關(guān)系代詞和關(guān)系副詞在定語從句中都充當(dāng)一定的句子成分：主語(who，which，that)；賓語(that，which，whom)；定語(whose，of which)；狀語(when，where，why)。
2.定語從句中關(guān)系詞的運(yùn)用
(1)關(guān)系代詞。
關(guān)系代詞的選擇一般需從三方面來考慮：①先行詞是指人還是指物；②關(guān)系代詞在從句中作主語、賓語還是定語；③該從句是限定性定語從句還是非限定性定語從句。
關(guān)系代詞作賓語時(shí)，一般可省略。如：
I know that he is a man who/that means what he says. (先行詞指人，關(guān)系代詞在限定性定語從句中作主語)
The man whom/that she met told her a lie. (先行詞指人，關(guān)系代詞在限定性定語從句中作賓語)
The watch which/that was lost has been found. (先行詞指物，關(guān)系代詞在限定性定語從句中作主語)
Here is the material which/that you need. (先行詞指物，關(guān)系代詞在限定性定語從句中作賓語)
He is the only one whose advice she may accept. (先行詞指人，關(guān)系代詞在限定性定語從句中作定語)
(2)關(guān)系副詞。
關(guān)系副詞的選擇主要看先行詞。如先行詞為表示時(shí)間的名詞，如time，day等，則用when；如先行詞為表示地點(diǎn)的名詞，如place，house，area等，則用where；如先行詞為reason，則用why。另外，where = in which，why = for which。例如：
I'll never forget the village where/in which I spent my childhood.
I don't know the reason why/for which he did that.
I'll never forget the day when I first entered the college.
(3)關(guān)系代詞that和 which的區(qū)別。①存在以下情況之一時(shí)，只能用that來引導(dǎo)定語從句：
第一，先行詞是all，everything，something，anything，little，nothing等不定代詞時(shí)；
第二，先行詞前有next，first，last，only，few，much，some，any，very，no等詞修飾時(shí)；
第三，先行詞前有形容詞最高級(jí)修飾時(shí)。例如：
I've explained everything (that)I can to you. This is the most beautiful city (that)I've ever been to.
�、诜窍薅ㄐ远ㄕZ從句一般不用that引導(dǎo)，且關(guān)系詞不可省略。例如：
His lecture, which bored everyone, ended at last.
The teacher's daughter, whom I met last month, sent me an e-mail.
(4)which和as引導(dǎo)定語從句的區(qū)別。在非限定性定語從句中，先行詞是整個(gè)句子時(shí)，一般用which或as來引導(dǎo)。which在從句中可充當(dāng)主語、賓語等，as在從句中一般只充當(dāng)主語。which與as引導(dǎo)此類定語從句的區(qū)別在于：which只能置于句中或句末，而as的位置比較靈活，既可置于句中、句末，又可置于句首。此外，as引導(dǎo)定語從句時(shí)還常和such，so，as或same連用，一般沒有明顯的先行詞，as一般可以譯為“正如，就像…那樣”。
例如：Water consists of hydrogen and oxygen, which/as is known to all.
As everybody knows, he is a good boy.
Such things as you have described are most important to me.
He is that kinds of man, such as people always meet.
I have the same dictionary as you have.
_____can be seen from the comparison of these figures, the principle involves the active participation of the patient in the modification of his condition.(1999.5)
�。跘］ As［B］ What［C］ That［D］ It
答案為［A］。As指代的是后面整句話的內(nèi)容，引導(dǎo)非限定性定語從句，其他選項(xiàng)只能引導(dǎo)主語從句。本句意為：正如我們從比較這些數(shù)字所看到的結(jié)果一樣，這項(xiàng)規(guī)則需要病人在治療時(shí)積極參與。
(5)關(guān)系代詞在定語從句中有時(shí)也作介詞的賓語。如果介詞被置于關(guān)系代詞前，一般只用介詞+which或介詞+whom，而不能用介詞+that來引導(dǎo)定語從句。如果介詞被置于從句句末，則可用that代替which或whom，且that這時(shí)可省去。
This is the coat on which she spent 500 dollars.
One of my classmates whom/that you are familiar with will come today.
Living in the central Australian desert has its problems, _____ obtaining water is not the least.(1994.3)
�。跘］ of which［B］ for what［C］ as［D］ whose
答案為［A］。題目中which的先行詞是problems，在which引導(dǎo)的非限定性定語從句中作介詞of的賓語，這時(shí)關(guān)系代詞要置于介詞后面，不能省略。介詞of表示所屬關(guān)系，of which指的是“在這些問題中”。［B］ 中的for表示原因，與題意不符；［C］ 和［D］ 也能引導(dǎo)定語從句，但都與句子的意思不符，所以只能選［A］。本句句意為：在澳大利亞中部，沙漠生活面臨許多問題，其中汲水是一個(gè)很嚴(yán)峻的問題。
