21. The picture in _____ honor of Lei Feng, a model for the Chinese people, is coming off. Use a nail to hold it in _____ place.
A. the; the B. the;/ C./;the D./;/
22. You might imagine that many such things would have happened in _____ was called "Cultural Revolution".
A. where B. when C. that D. what
23. It is written clearly in the requirements that all passengers' parcels _____ before boarding the plane.
A. will check B. be checked C. are to check D. are checking
