定语从句

　　I.it／one ／that三者均可用作代词,指代前面提到的名词.一般说来,it指代同名同物; one与that则指代同名异物.

　　I have lost my umbrella; I'm looking for it.（该句中it就是指前面的my umbrella）

　　I have lost my umbrella; I think I must buy one.（one在该句中表泛指,因为my umbrella已经丢了）

　　The umbrella you bought is cheaper than that I bought.（替代词that在该句中特指the umbrella I bought,以区别the umbrella you bought）

　　II.one与that虽可用来指代同名异物,但one为泛指,相当于a／an＋名词; that为特指,相当于the ＋名词.所以one所指代的名词的修饰语一般为 a／an ／some ／any; that所指代的名词的修饰语往往是the ／this ／that.

　　A chair made of steel is stronger than one made of wood.（该句中one可以换成a chair）

　　The water in the cup is hotter than that in the pot.（该句中that可以换成 the water）

　　III.one只能代替可数名词单数,代替可数名词复数时用ones; that既可以代替不可数名词也可以代替可数名词单数,代替可数名词复数时用 those.

　　I like this pen more than that one.（one代替可数名词单数pen）

　　There were a few young people and some older ones in the house.（ones代替可数名词复数people）

　　Mary's handwriting is far better than that of Peter.（that代替不可数名词 handwriting）

　　These pictures are more beautiful than those.（those代替可数名词复数 pictures）

　　IV.one既可代替事物,也可代替人,that只能代替事物而不能代替人.有时可以用the one或the ones代替that或those.

　　The one ／That on the table is mine.（该句中The one代替事物,并且也可以用That）

　　He is the teacher,the one who is loved by the students.（该句中the one代替人,不能用that）

　　He advised the farmers to choose the best seed-heads,the ones ／those that had the best color.（该句中the ones代替事物,并且也可以用those）

　　V.one一般有前置修饰语,有时也可有后置修饰语或不用修饰语.而 that不能有前置修饰语,但可有后置修饰语.

　　Cook was a strict but good captain,one who took good care of his sailors.

　　The water in the well is cleaner than that in the river.

　　VI.it可以替代句中的不定式或从句等,充当形式主语或形式宾语.one与that均无此用法.

　　It is known to everybody that the moon travels around the earth once every month.

　　I found it hard to get on with her.

　　VII.it与that均可以替代上文全句的内容或部分内容,而one ／ones则不可以

　　where定语从句

　　where在定语从句中的用法

　　1.先行词表示具体地点的,并在在定语从句中做状语的（不做主语,表语和宾语）,用where引导定语从句.例如：this is the house where i once lived.

　　2.先行词是表示抽象地点的如point,case,postion,condtion,activity,situation,job等,并作状语用where引导.

　　You reach a point where medicine cant help.你已到了药物无法治疗的地步.

　　Its put me in a position where I cant afford to take the job.这使我陷入一种不能接受此工作的境地.

　　She wants a job where her management skills can be put to good use.她想找一份能将她的管理技能派上用场的工作.

　　判断关系代词与关系副词

　　方法一： 用关系代词，还是关系副词完全取决于从句中的谓语动词。及物动词后面无宾语，就必须要 求用关系代词。例如：

　　（错） This is the mountain village where I visited last year.

　　（错） I will never forget the days when I spent in the countryside.

　　（对） This is the mountain village (which) I visited last year.

　　（对） I'll never forget the days (which) I spent in the countryside.

　　习惯上总把表地点或时间的名词与关系副词 where, when联系在一起。此两题错在关系词的误用上。

　　方法二： 准确判断先行词在定语从句中的成分(主、谓、宾、定、状)，也能正确选择出关系代词/关系 副词.先行词在从句中作主、定、宾语时，应选择关系代词；先行词在从句中作状语时，应选 择关系副词。

　　例如：（对）Is this the museum which you visited a few days ago?

　　（对）Is this the museum where the exhibition was held?

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