A. To keep out boats that are too large for the canal. B. To measure the tonnage of canal boats. C. To load and unload the cargo. D. To change the depth of the watch 参考答案:D 答案解析:最后一段详细论述lock canal，指出这种运河的用处是改变水位方便船只通过。
第32题: [单项选择]What is the purpose of the woman’s message A. To ask when an employee will return to work B. To inquire about the status of a patient C. To find out about visiting hours at the hospital D. To show her support for an employee 参考答案:D 答案解析:[听力原文] 71-73 Questions 71～73 refer to the following telephone message． 有关向住院的同事问候的电话留言
