主語(yǔ)從句
用作主語(yǔ)的從句叫主語(yǔ)從句。
(That the earth goes around the sun) is known to all.
(How this happened) is not clear to anyone.
(Whoever comes) is welcome.
(When we shall have our sports meeting) is still a question.
(Whether he will come today) is still unknown.
注意：
1. 主語(yǔ)從句是特殊疑問(wèn)句，應(yīng)該用特殊疑問(wèn)詞加陳述句語(yǔ)序。
2. that引導(dǎo)的主語(yǔ)從句放在句首，不可省略that。
3. 主語(yǔ)從句常用it作形式主語(yǔ)，真正的主語(yǔ)放在后面，這時(shí)that可省略。
It's a pity (that) you missed such a good opportunity.
It's still a question when we shall buy the new equipment.
It's still unknown whether he will come or not.
4. It is + P.P.+ that ; It + Vi + that，It作形式主語(yǔ)。
It is said that the president will visit our company.
It seems that he has caught a cold.