这也是常见问题了,参考下面的：
宾语从句（一） 宾语从句在复合句中作主句的宾语.宾语从句常由that引导,在口语中常省略.当主句中谓语动词是现在或将来时态时,从句中谓语动词不受主句中谓语动词时态的 影响,按需要可以使用任何时态.如：She says (that) she works from Monday to Friday.她说她从周一至周五上班.（从句是一般现在时） She says (that) she will leave a message on his desk.她说她要在他桌子上留个便条.（从句是一般将来时） She says (that) she has never been to Mount Emei.她说她从来没有去过峨眉山.（从句是现在完成时） 当主句谓语是过去时态,从句中的时态一般用表示过去的某种时态.如：He said there were no classes yesterday afternoon.他说昨天下午没有课.（从句是一般过去时） He said (that) he was going to take care of the baby.他说他会去照看这个婴儿.（从句是过去将来时） He said (that) they were having a meeting at that time.他说他们那时正在开会.（从句是过去进行时） *当主句谓语是过去时态,而宾语从句叙述某一客观真理（事实）时,宾语从句的时态则用一般现在时.如：The teacher told us(that) nothing is difficult if you put your heart into it.老师告诉我们世上无难事只怕有心人.She said (that) her father is twenty-eight years older than her.她说她父亲比她大二十八岁.He said that light travels much faster than sound.他说光传播比声音传播快得多.
宾语从句（二） 由连接代词或连接副词引导的宾语从句.引出名词性从句的连词whether和if,在引出宾语从句时,用法和意义相同.但是只能引出宾语从句和不在句首的主语从句,而whether除了引出宾语从句外,还可引出主语从句、表语从句和同位语从句.例如：We don't know whether (if) it is right.我们不知道它是否正确.The question is whether she should do that.问题在于她是否应该做那件事.Whether it is true remains a question.是真是假还是个问题.试比较：当if从句处在主句之后作“是否”讲时,引出的是宾语从句.例如：I don't know if it is true.我不知道这事是否真实.当if从句在主句之前作“如果”讲,则引出状语从句.例如：I shall go there if I have time.如果我有时间,我将到那儿去.
定语从句（Attributive Clauses）在句中做定语,修饰一个名词或代词,被修饰的名词,词组或代词即先行词.定语从句通常出现在先行词之后,由关系词（关系代词或关系副词）引出.
关系代词有：who,whom,whose,that,which等.
关系副词有：when,where,why等.
关系代词所代替的先行词是人或物的名词或代词,并在句中充当主语、宾语、定语等成分.关系代词在定语从句中作主语时,从句谓语动词的人称和数要和先行词保持一致.
1）who,whom,that
这些词代替的先行词是人的名词或代词,在从句中所起作用如下：
Is he the man who/that wants to see you?
他就是你想见的人吗?（who/that在从句中作主语）
He is the man whom/ that I saw yesterday.
他就是我昨天见的那个人.（whom/that在从句中作宾语）
2) Whose 用来指人或物,(只用作定语,若指物,它还可以同of which互换）,例如：
They rushed over to help the man whose car had broken down.那人车坏了,大家都跑过去帮忙.
Please pass me the book whose (of which) cover is green.请递给我那本绿皮的书.
3）which,that
它们所代替的先行词是事物的名词或代词,在从句中可作主语、宾语等,例如：
A prosperity which / that had never been seen before appears in the countryside.农村出现了前所未有的繁荣.（which / that在句中作主语）
The package (which / that) you are carrying is about to come unwrapped.你拿的包快散了.(which / that在句中作宾语）
关系副词可代替的先行词是时间、地点或理由的名词,在从句中作状语.
1）when,where,why
关系副词when,where,why的含义相当于"介词+ which"结构,因此常常和"介词+ which"结构交替使用,例如：
There are occasions when (on which) one must yield.任何人都有不得不屈服的时候.
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?这就是他拒绝我们帮助他的理由吗?
2）that代替关系副词
that可以用于表示时间、地点、方式、理由的名词后取代when,where,why和"介词+ which"引导的定语从句,在口语中that常被省略,例如：
His father died the year (that / when / in which) he was born.他父亲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过的地方.