这种结构:It作形式主语,后跟形容词加that用做虚拟语气时,that后均为(should )do,should可以省略,如:It's important that you (should) work hard. 类似结构还有:It's suggested/believed/said that...
后面加 should + 动词原形 (或 should + have + 过去分词)或只有动词原型(省略should)
如:It is important that we should speak politely. 我们说话要有礼貌,这的很重要的。
should + should +动词原形
It's important that they (should) eat healthy food
should可以省略