题目

图中所示的抛物线形桥，当找顶离水面4m时，水面宽8m，水面上升3米，水面宽度减少多少? 答案：解：建立如图所示坐标系. 则可得过点(4，−4) 设解析式为y=ax2 代入(4，−4)得a=−14. 所以解析式为y=−14x2. 把y=1代入，得x=±2， 则水面的宽减少8−4=4米 完形填空。        Dick was a clever boy, but his parents were poor, so he had to work   1   his spare time and during hisholidays to   2   his education.   3   this, he   4   get to the university, but it was   5   expensive to study therethat during the holiday he found   6   necessary to get two jobs   7   the same time   8   make enough money   9   his studies.        One summer he managed to  10  a job in a butcher's shop (肉店) during  11 , and another in a hospital  12 . In the shop, he learnt to cut meat quite nicely, so the butcher often  13  him doing all the serving  14  he went to the back room to do the accounts (账目). In the hospital,  15 , he was, of course, allowed to dothe simplest jobs,  16  helping to lift people and to  17  them from one part of the hospital to another. Both at the butcher's shop and at the hospital, Dick had to  18  white clothes.        One evening at the hospital, Dick had to help a woman from her bed to the place  19  she was to have an operation. The woman was already feeling frightened at the  20  of the operation before he came to get her, but when she saw Dick, she fainted away (晕过去). (     )1. A. on             (     )2. A. pay for        (     )3. A. Instead         (     )4. A. tried to       (     )5. A. too             (     )6. A. it's          (     )7. A. at              (     )8. A. in order that  (     )9. A. with            (     )10. A. look for        (     )11. A. day time        (     )12. A. at night       (     )13. A. let             (     )14. A. while           (     )15. A. on other hand  (     )16. A. like            (     )17. A. want            (     )18. A. on             (     )19. A. that           (     )20. A. thought        B. in              B. pay off         B. Instead of      B. hope to         B. very            B. this           B. on              B. as to           B. for             B. find            B. the night      B. at noon        B. left           B. as soon as     B. on another hand   B. for            B. fetch           B. wear            B. which           B. time           C. at                   C. pay to               C. In spite of          C. wanted to            C. so                   C. that                C. by                  C. as so to            C. to                  C. reach               C. the night time       C. in the morning      C. made                 C. after                C. on the second hand  C. as                   C. carry               C. be on                C. where                C. end                  D. with               D. pay back           D. In need of         D. was anxious to     D. much               D. it                 D. for                D. so as to           D. because of         D. take               D. the daytime        D. in the daytime     D. had                D. until              D. on the other hand        D. from               D. raise              D. dress on           D. there              D. beginning