高中“主语从句”的用法
Whether he will join us won't make too much difference. 他是否加入我们不会有多大的影响。
= It won't make too much difference whether he will join us.
When they will come hasn't been make public.他们什么时候来还没宣布。
= It hasn't been made public when they will come.
常见的it作形式主语的4种句型如下图：
句型1：It be adj that从句
能用于这种句型的形容词有：natural, strange, obvious, true, possible, impossible, clear, likely, surprising等。
It’s likely that he told her everything.
句型2：It be名that 从句
常用于该句型的名词词组有：a pity, a shame, a fact, an honor, good news等。
It’s a pity that we can’t go.
句型3：It seems/ happens/ occurs that从句
It happened that I wasn’t there that day.
句型4：It be过去分词that从句
常用的过去分词有：said, reported, hoped, believed, expected, decided, proved等。
It has been proved that eating vegetables in childhood helps to protect you against serious illnesses in later life.
特别提醒：
what, whatever, whoever引导的主语从句不用it作形式主语。
Whoever breaks the law should be punished.
该句不能说：It should be punished whoever breaks the law.句中的whoever≠ No matter who，该句可转换为定语从句：Anybody who breaks the law, they should be punished.
主语从句是高中英语学习中的一个难点，我们在学习中要抓住这4个句型和3个特殊引导词，在运用中理解，在理解中感悟，那么，我们就能准确地掌握主语从句的精髓，运用灵活，为自己的英语写作增添亮色！但愿我能帮到大家！如有英语学习中的疑问，请加我的微信（wl730611）或我的微信公众号（wls730611）。
