浮选（）流程主要指流程的主体结构。
A、生产
B、工艺
C、原则
D、生产技术
参考答案：C
Li Lei decided . [ ]
A. to not stay with his parents
B. not to stay with his parents
C. staying with his parents
D. not staying with his parents
电压超过（）V的开关控制盒，必须要有“高压危险”标志。
A.300
B.380
C.500
D.600
