21.All the students are looking forward to the first ____to take the college Entrance Examination .

  A. measure         B. attempt               C. purpose        D. desire

22.It took us several hours to make the old man _____of the safey of travelling by air.

A. believed        B. convinced                   C. informed        D. persuaded    

23.It’s high time that you _____even harder at your lessons as the exam is around the corner .

A. work           B. will wor k              C. worked         D. have to work