中考英语之主语从句

主语从句是指在复合句中充当主语的从句。简单来说，就是用一句话来充当主语。

例句：

That he will come is certain. (他会来，这是确定的。)

What he said is true. (他说的是真的。)

结构：主语从句 + 谓语动词 + 其他成分

考点1：引导词的选择

主语从句的引导词与宾语从句类似，根据从句的类型和意义选择：

that引导的主语从句

that无意义，不能省略

That he is honest is known to all.

whether表示“是否”

Whether he will come is not known.

what表示“所……的事情/东西”What he needs is more time.

who表示“谁”Who will go is still a question.

when/where/why/how表示时间/地点/原因/方式When he left is a mystery.

注意：主语从句中，that 不能省略，而宾语从句中的 that 可以省略。

考点2：形式主语 it

为了避免句子“头重脚轻”，英语中常用 it 作形式主语，而把真正的主语从句放在句末。

结构：It + 谓语 + 主语从句

常见句型

It + be + 形容词 + that...

It's clear that he is lying.

It + be + 名词 + that...

It's a pity that you can't come.

It + be + 过去分词 + that...

It is said that he is ill.

It + 动词 + that...

It seems that she is happy.

常见形容词：clear, obvious, certain, true, important, necessary, possible, likely

常见名词：a pity, a shame, a fact, an honor, no wonder

常见动词被动式：said, reported, believed, known, thought

对比：

That he will come is certain. (头重脚轻，不自然)

It is certain that he will come. (形式主语，更自然)

考点3：主谓一致

主语从句作主语时，谓语动词通常用单数形式。

That he is late is not surprising. (他来晚了并不令人惊讶。)

What he needs is more time. (他需要的是更多时间。)

What they need are books. (注意：what引导的主语从句，谓语动词的数取决于表语——若表语是复数，谓语也可用复数)

特殊注意：what 引导的主语从句，谓语动词的数根据表语决定：

What he needs is a book. (表语单数 → 谓语单数)

What he needs are books. (表语复数 → 谓语复数)

考点4：whether 与 if 的区别

在主语从句中，表示“是否”只能用 whether，不能用 if。

Whether he will come is unknown. (✅)

If he will come is unknown. (❌)

总结：whether 可用于主语从句、表语从句、同位语从句、介词后的宾语从句；if 只能用于动词后的宾语从句。

1.______ is known to us all that the earth goes around the sun.

A. That     B. It      C. This      D. What

1. ______ we need is more time and more help.

A. That   B. What   C. Which   D. Whether

3.What she said ______ true.

A. be     B. am    C. is     D. are

距2026年苏州中考76天

1. B【解析】 本句真正的主语是“that the earth goes around the sun”，用 it 作形式主语，避免头重脚轻。It is known to us all that... 是固定句型。

2. B【解析】 主语从句中缺少宾语（need的宾语），表示“所……的东西”，应用 what 引导。that 在从句中不作成分；which 表示“哪一个”；whether 表示“是否”，均不符合。

3. C【解析】 what 引导的主语从句作主语，谓语动词通常用单数形式，故选 is。