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.