It 做形式主语 Its necessary for the young to master two foreign language. Its a waste of time talking to her any more. Its a pity that you missed the exciting football match. 动词不定式 动名词 从 句 形式主语It 作为形式主语的用法 当 不定式、动名词、从句 等用作 句子主语时，为保持句子平衡，通 常把真正的主语放在句末，而在句 首使用形式主语it.拒绝是令人遗憾的. 记住这一点是很重要的. Its a pity to refuse. Its very improtant to remember this 一、代替动词不定式做形式主语It +be +adj.+ （for sb. ）to do sth. 此处adj. 通常为描述事件的形容词：easy ， difficult ，hard ，necessary ，impossible ， important ，natural, likely ，obvious ，useful
