is known to us all is that the theme of Shanghai World Expo is “Better City Better Life”

问题补充：

is known to us all is that the theme of Shanghai World Expo is “Better City, Better Life”.

A. It

B. That

C. Which

D. What

答案：

A. It

B. That

C. Which

(答案→)D. What

解析：考查主语从句。观察句子结构，不难发现第二个is前面是一个主语从句，从句中缺主语，故使用连接代词what。句意：众所周知，上海世博会的主题是“城市让生活更美好”。