21.Passengers are permitted only one piece of hand luggage onto the plane.
A. to carry B. carrying C. to be carried D. being carried
22. We ______on this project for four hours. Let’s have a rest.
A. are working B. have been working C. worked D. had worked
23. ______ in 1955, Disneyland in California is regarded by many as the original fun park.
A. Opened B. Having opened C. Opening D. Being opened