If you really have to leave during the meeting, you’d better leave ____ the back door.
( ) 15. The building is ________.
( ) 14. The students handed in their test papers to the teacher _______ .
( ) 13. It’s well known to us all ______ Beijing will _____ the 2008 Olympic Games.
( ) 12. He needs one more stamp before his collection __________.
( ) 11. ________ fresh air, people may start to feel sick. So make sure you open the windows while working.