15．Danby left a message with the professor ______ he would call again in the afternoon.

　　 A. who　　　　　 B. that　　　　 　C. as　　　　　　　 D. which

14．_____ the catastrophe happened that the local government realized the importance of substantial development.

　A．It was until　　　　 B．Not until　　　 C．Until　　　　　　　　　 D．It was not until

13．-There will be a talk show this time tomorrow．Would you go with me?

　　　 -I'm sorry, but I ______ an important meeting．

　　　 A．have attended　　　　　　　　　　 B. will be attending

　　　 C．am about to attend　　　　　　　 　　　 D. will attend

12．______ is known to us all , the old scientist,______ life was hard in the past, still works hard in his eighties.

　　 A. It; whom　　　　　 B.As; whom　　 C. As; whose　　　　　 D. What; whom

11．The ______ flights between the mainland of China and Taiwan will benefit more travelers.

　A．common　　　　　　　　 B．normal　　　 C．average　　　　　　　　　 D．regular