主语从句有三类:
由what等代词引导的主语从句: what表示“所……的(东西)”, 在结构上等于一个名词加一个定语从句; whatever表示“所……的一切”; whoever表示“一切……的人”.
What you need is more practice
What is hard is to do good all one’s life and never do anything bad.
Whatever was said here must be kept secret.
Whatever I have is at your service.
Whoever comes will be welcome.
Whoever fails to see this will make a big blunder.
由连词that引起的主语从句: 这类主语从句在大多数情况下都放到句子后部去, 而用代词it做形式上的主语:
That we need more equipment is quite obvious.
It is impossible that I may not able to come.
It doesn't seem likely that she will be here.
在口语中连词that有时可以省略掉:
It's good you're so considerate.
It's a pity you missed such a fine talk.
由连接代词或连接副词(或whether)引起的主语从句: 这类主语从句, 也可以放到句子后部去, 前面用it做形式上的主语.
When we shall have our sports meet is still a question.
It is still a question when we shall have our sports meet.
Whether he will join us won't make too much difference.
It won't make too much difference whether he will join us.
2宾语从句: 和主语从句及表语从句一样, 宾语从句也有以上三类.
a) 连接代词或副词引导的从句只是在某些动词后能用作宾语.
Tell me what you want.
I just can't imagine how he could have done such a thing.
Have you decided whom you are to nominate as your candidate.
能跟这类宾语从句的常见动词有: see, say, tell, ask, answer, know, decide, find out, imagine, suggest, doubt, wonder, show, discover, discuss, understand, inform, advise等. 这种动词后也常用whether或if引导的从与作宾语:
I don't know whether these figure are accurate.
I'm wondering if the letter is overweight.
这种从句有时前面可以有另一个宾语:
Has she informed you when they are to hold the meeting?
Please advise me which book I should read first.
有时这种从句也可用作及词的宾语:
Whether that is a good solution depends on how you look at it.
He was not conscious of what an important discovery he had made.
I was curious as to what he would say next.
b) 用that引导的从句作宾语的情形最为普遍, 在很多动词如boast, say, think, insist, wish, hope, suppose, see, believe, agree, acknowledge, admit, deny, expect, explain, confess, order, command, suspect, dream, suggest, propose, know, mean, notice, prefer, request, require, report, urge, 以及doubt的否定和疑问式后面都可以用它.