16.Has it been announced________ the planes are to take off?　　　　 whether/if

15.The suggestion________ students should learn some practical knowledge is worth considering. 　　　　　　　　　　　　　　　　　　　　　　　　　that

14. Einstein's most famous theory is ____ we call the Theory of Relativity. 　what

13.The reason 　　he was late was ____ he had taken a wrong bus. 　　why，that

12.She dresses well，but the trouble is________ the clothes she is wearing don’t go with each other very well.　　　　　　　　　　　　　　　　　　　 　that

11.The reason for his success is _______ he worked hard. 　　　　　　that　　

10. The nurse asked them not sit ______ they were. 　　　　　　　　　where

9. This museum is not ______ it was ten years ago. 　　　　　　　　　what

8. The problem is not ___ we leave, but ____ we can get there.　　 when; how

7. It looks ______ it's going to rain.　 　　　　　　　　　　　　　　as if