21. __________ latest news from Nanjing is that _____ old people can get on a public bus without paying the fare.
A. The; 不填 B. The; the C. 不填; the D. 不填； 不填
22. -- So far _____________.
-- That’s too bad.
A. we received no letter from him B. he won’t send us any message
C. nothing from him has been received D. we won’t hear from him
23. Doctors say it will be many years ___________ scientists develop an effective treatment for AIDS.
A. when B. since C. before D. as
