门机的A、B、C级检保间隔期为多少运行小时?
参考答案:A级定期检保间隔期为200运行小时,B级检保的间隔期为1600运行小时,C级检保的间隔期为4800运行小时。
— ______ did you see a cat run from behind the door?
— As soon as I entered the room.[ ]
A. What
B. When
C. Where
D. Why
表面安装技术是SMT的核心,()是决定表面贴装产品质量的关键。
A.印刷
B.贴片
C.焊接
D.检测