15．-Don't make any noise in the living room! My baby is sleeping．

　-_　　 _　 _.

　A．Excuse me, I'm wrong　　　　　　 B．No, I don't

　C．Sorry, I won't　　　　　　　　　　 D．Certainly, I won't

14．The fact has worried many scientists _　　 __ the earth is becoming warmer and warmer these years．

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

13．The building around the corner caught Fire last night．The police are now _　　 __ the matter．

　A．seeing through　　　　　　 　　　B．working out

　C．looking into　　　　　　　　　　　 D．watching over

12．We consider it necessary that a plan _　　 __　 before doing something．

　A．to be made　　　 B．is made　　　　 C．will be made　 D．be made

11．I have been living in the United States for twenty years, but seldom _　　 __ so lonely as now．

　A．have I felt　　　 B．I had felt　　　 C．I have felt　　　 D．had I felt