it is 跟动词ing 还是to do

It's adj+to do sth.

在这个句型中，it是形式主语，代替后面的动词不定式.

例如：It's important to learn English well.学好英语很重要.

①it is fun to do sth

It could be fun to watch them play. 看他们玩会很有趣。

It’s fun to ski down a mountain. 滑雪下山很有趣。

It's fun to be in a large city at Christmastime. 大城市圣诞节期间非常好玩。

It is more fun to go with someone than to go alone. 偕伴同去比自己独自去好玩。

②it is fun doing sth

It’s fun working for him. 为他工作很有意思。

It’s no fun eating on your own. 一个人吃饭没意思。

It’s fun being taken to the zoo. 被带去看动物园真有意思。

It’s not much fun going to a party alone. 独自一人去参加聚会没什么意思。

It’s no good/use… -ing and It is worth …-ing.常用-ing， 其他时候为非正规表达。1) It’s no good talking to him – he never listens.2) It’s no use expecting her to say thank-you.3) It’s no use trying to explain – I’m not interested.

It is后面既可以跟动词的ing形式 也可以跟动词不定式to do 。但是后面跟ing形式和动词不定式 所表达的内在意义不一样 ，后接动词的ing形式时 表达现在 进行时态 ，强调动作 正在进行或发生，而接动词不定式时 表示将来的动作 。如：It is raining outside 。 外面正在下雨

It's to rain tomorrow according to the weather report

is 后面的动词 不一定要用 ing 形式，要具体情况具体分析的呢 当为be+to do 为将要做某事，或是祈使句 在此What you've got to do is turn around and say :" Watch me".为一句祈使句，口头用语呢 turn around and say 是前面what you've got to do

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