20．Measures have been taken to solve the problem, but it may be some time ____ the situation improves．

　　　 A．since　　 　　　　　 B．when　　 　　　　　 C．unless　 　　　　　　　 D．before

19．Hoping he would not disturb his sleeping father, Bob stole in, ____ and waited for him to wake up

　　　 A．didn’t speak　　　　 B．not to speak　 　　 C．not speak 　　　　　 D．not spoke

18．-What do you think of last Friday’s charity pop concert, Tim?

　　　 -It was a great success as a whole．Actually we ___ with half of the money collected．

　 　　 A．would have been satisfied　　 　　　　　　　 B．were satisfied　　

　　　 C．would be satisfied　　 　　　　　　　　　　　　 D．will be satisfied

17．____the sketch(short funny play) of Xiao Shenyang made a _____has been known to us all．

　 　 A．That; hit　　 　　　 B．What; strike　　　　 C．Why; beat 　　　　　 D．Which; knock