司机在工作中对机械设备要坚持的“十字作业法”：（）。
参考答案：清洁、润滑、调整、紧固、防腐
计算题
1. What percentage of area is shaded?
Answer: _ .
2. If a group of 6 people have an average age of 21, and each person is half the age of the next person,
what are the ages of the 6 people?
脾合胃
