21. apple four hundred years ago led to the law of gravity while ____ apple designed by Steve Jobs has changed our life greatly.
A. The; an B. An; the C. An; an D. The; 不填
22. It's ________ taking the trouble to explain a job fully to new employees.
A. worth B. worthwhile C. worthy D. valuable
23. Having been ill in bed for nearly a month, he had a hard time _______ the exam.
A. pass B. to pass C. passed D. passing
24. —The education system _______ the teachers is to answer for the overburden on the students.
—I agree. I hope the reform _______in our country at present will bring about the desired result.
A. rather than; being carried out B. other than; carried out
C. more than; to carry out D. less than; carrying out
25. John studied hard before the examination and it ______. He came first.
A. paid back B. paid off C. paid for D. paid out
26. Maybe if I _______ science, and not art then, I would be able to give you more help.
A. studied B .would study C. had studied D. was studying
