表語從句
構成方式：
若從句為陳述句，直接加that;
若從句為特殊疑問句：直接保留特殊疑問詞，后面的句子變成陳述句語序;
若從句為一般疑問句：先把一般疑問句變成陳述句語序，然后在其前加上weather或者if;
eg：China is no longer what she used to be.
The question is who is responsible for what has happened.
(4)主語從句：主語變成一個句子
構成方式： 若從句為陳述句，直接加that;
若從句為特殊疑問句：直接保留特殊疑問詞，后面的句子變成陳述句語序;
若從句為一般疑問句：先把一般疑問句變成陳述句語序，然后在其前加上whether或者if;
位置：直接置于句首;
eg：That the college will take in more students is true.
Whether he will come or not hasn't been decided.
Why he isn't here is not clear to everyone.
it 做形式主語的情況：
(1)It is+名詞+主語從句;
eg：It is a pity that you should have to leave.
(2)It is+形容詞+主語從句;
eg：It is clear that the whole project is due to failure.
如果是It is necessary/important/strange/natural+that引導的主語從句，從句中的謂語動詞一定要用should+動詞原形;
eg：It is necessary that one should master the skills of operating computer.
(3)It is+過去分詞+主語從句;It is said/planted/expected…
eg：It is said that President Bush will visit our school next week.
(4)It is+不及物動詞+形容詞表語形式+主語從句;
eg：It seemed certain that he will win the prize.