主语从句

    用作主语的从句叫主语从句。

    （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.主语从句是特殊疑问句，应该用特殊疑问词加陈述句语序。

    2. that 引导的主语从句放在句首，不可省略that.

    3.主语从句常用it作形式主语，真正的主语放在后面，这时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作形式主语。

    It is said that the president will visit our company. It seems that
he has caught a cold.