二．单项选择（每小题1分，共20分）
( )21. Don’t go and bother him. He _____ in the room.
A. writes B. has written C. is writing D. has been writing
( )22. She will have a holiday as soon as she _______ the work next week.
A. finishes B. doesn’t finish C. will finish D. won’t finish
( )23. Our physics teacher told us that light _______ faster than sound.
A. travel B. travels C. is travelling D. has travelled
