21. In communication, a smile is usually _____ strong sign of a friendly and _____ open attitude.
A. the; / B. a; an C. a; / D. the; an
22. You don’t have to worry about the journey because I have made a ______ on the Indian Pacific train to Perth.
A. reserve B. book C. preparation D. reservation
23. In the plane crash accident, the chance of the pilots’ survival is ______.
A. slight B. slim C. smooth D. spare
