The World Expo 2010 is being held at a time        the world is looking for a new kind of balance between nature and cities．

         A．which        B．where         C．when         D．that

The World Expo 2010 is being held at a time        the world is looking for a new kind of balance between nature and cities．

         A．when                       B．where                       C．which                      D．that

The World Expo 2010 is being held at a time        the world is looking for a new kind of balance between nature and cities．

       A．when                 B．where                 C．which                D．that

The World Expo 2010 is being held at a time 　　　 the world is looking for a new kind of balance between nature and cities．

　 A．when 　　　 B．where　　　 C．which 　　　 D．that

The World Expo 2010 is being held at a time        the world is looking for a new kind of balance between nature and cities．

1. A.
   when
2. B.
   where
3. C.
   which
4. D.
   that