第四，同位语从句。

　　Eg: It is an undeniable fact that environmental pollution becomes increasingly serious.环境污染变得越来越严重是不可否认的事实。

　　Eg: No one can deny the basic fact that it is impossible for average workers to masteｒ those high-technology skills easily.

　　没有人能否认这一基本事实：对于一般工人来讲，轻松掌握这些技术是不可能的。

　　第五，主语从句。

　　Eg: What has caught our attention is /It is noticeable that the environment in both the rural and urban areas is deteriorating.

　　值得注意的是农村和城市的生态环境都在不断恶化。

　　Eg: It is universally acknowledged that environmental pollution becomes one of the most serious problems in China or even the world as a whole. source:veduchina

　　众所周知，环境污染问题是中国乃至世界面临的最为严重的问题之一。

　　第六，强调句: It is + 被强调的内容 + that

　　Eg: It is cars and factories that release a great deal of gases, polluting the environment.

　　汽车和工厂排放大量的废气，使得环境被污染。

　　第七，倒装句。

　　Eg: Only if the government will take some appropriate measures, will this intractable problem be tackled.

　　只有政府采取适当的措施，这个棘手的问题才能被解决。