起重架子常用的材料是()。
A、高速钢
B、铸铁
C、结构钢
D、硬铝
参考答案:C
When someone helps you, don't forget to say " ____________ ". [ ]
A. I'm sorry.
B. That's all right.
C. Goodbye.
D. Thank you.
过程定义是企业资源管理所需要的逻辑相关的一组活动和【 】。