It is+n.（a pity/a shame/a good idea/no wonder/…)+主语从句
使用pity 和shame 时，从句中一般用（should+）动词原形，表示“竟然”
如果没有这个意思，就不需要用虚拟语气
It is a pity that such a thing (should) happen in your class.
It is a pity that he is ill.
It is (high) time+that sb. did sth./that sb.should do sth.（注：should不可省略）
It is+adj.(clear/obvious/likely/true/…)+主语从句
It is+adj.(necessary/important/natural/strange/urgent/impossible等表惊奇或理应如此)
+that+ sb.+(should)+动词原形
It is+过去分词（said/reported/believed/thought/announced/…）+主语从句
It+不及物动词+主语从句
It doesn't matter whether…
It+及物动词+宾语+主语从句
It worries/shocks sb. that…
It occurred to sb. that…
