擅自从事电梯（）的，责令停止违法行为，处一万元以上十万元以下罚款。
A.改造
B.修理
C.维护保养
D.生产
参考答案：C
---I think you can ________ money by yourself to buy a birthday present for your mother.
---OK. I’ll try. I’ll not let a penny waste.
A．spend
B．save
C．cost
D．leave
冲击力有哪些分类？
