加料起重机主小车下部的旋转部分，方形主柱的铜（或铁）套磨损达厚度（）时应报废。
A、5％
B、10％
C、15％
D、25％
参考答案：D
Duty is an act or a course of action that people _____ you to take by social customs, law or religion. [ ]
A. persuade
B. request
C. instruct
D. expect
