(2) It is + 形容词 + 从句
　　It is natural that… 很自然…
　　It is strange that… 奇怪的是…
　　(3) It is + 不及物动词 + 从句
　　It seems that… 似乎…
　　It happened that… 碰巧…
　　It appears that… 似乎…