一、that,what和which
1. that引導名詞性從句時只起連接從句的作用,本身沒有任何意義,因此在從句中不充當任何句子成分,它的使用須注意以下幾點:
A. 引導賓語從句時,that?？墒÷?但如果主句后跟有并列賓語從句時,只能省略第一個that;若賓語從句前插有別的從句時,that也不能省略。例如:
He told me (that) he was all right and that he would come to see me when he was free. 他告訴我說他很好,并說在他有空時來看我。

B. that引導主語從句位于句首時不可省略.如果it作形式主語,而that從句置于句末, 這時that可以省略。例如:
That he has lost his work is not true. 他丟了工作不是真的。
=It is not true (that) he has lost his work.

C.當主語為the reason時,注意應用that 引導其表語從句,不能受漢語影響而誤用because。例如:
The reason why he was late was that he missed the early bus. 他遲到的原因是他沒趕上早班車.(此句中的that不可用because代替)

D.引導同位語從句時,切不可錯用which。例如:
Word has come that some American guests will come to visit our school next week. 有消息說下周將有一些美國客人來我校參觀。

2. what與which引導名詞性從句時都在從句中充當句子的某一成份,如主語、表語、賓語或定語,其區(qū)別是:what表示泛指的事物,常譯為"什么"或"所……的事物", whatever是它的強語勢"無論什么";which表示特定事物中的"哪一個(些)",一般情況下在從句中充當定語,后接名詞,在一定的語境中,它所修飾的名詞可以省略,whichever是它的強語勢"無論哪一個(些)"。例如:

I believe what (whatever) he says. 我相信他說的(不管他說什么我都相信)。
I will give her which (whichever) book she likes on the shelf. 這個書架上的(任何一本)書,只要她喜歡,我都會給她。

二、who,whoever,whom和whomever
在引導名詞性從句時,在句中作主語時用who,意思是"誰",含有疑問意味,whoever是它的強語勢"無論誰",不含有疑問意味。作賓語時用whom, 其相應強語勢為whomever。判別時要根據(jù)句意以及在句中的語法功能來決定該用哪個引導詞。例如:

Who has taken away my bag is unknown.誰拿走了我的包還不知道。(若用Whoever顯然句意不通)
Whoever wants to see this film can go with us tonight. 無論誰想看這部電影今晚可以和我們一起去.(Whoever wants 相當于Anybody who wants,意為"凡是想……的人"。這里不可換為Who。)
Have you decided whom you are to nominate as your candidate? 你們是否已經(jīng)決定提名誰作侯選人了?
You can give the ticket to whomever you like. 你可以把票給任何你想給的人。