For many citis in the world ,there is no room to spread out further ,( )

问题描述:

For many citis in the world ,there is no room to spread out further ,( )
For many citis in the world ,there is no room to spread out further,( ) which New York is an example.
为什么填 of 而不是 for

句子主体是讲many cities,然后举例说明,应该是one of them
这个句子拆成独立句子就是:
For many cities in the world,there is no room to spread out further.New York is an example of them.