设计接地网时,应验算( )和跨步电位差。
A.接触电势差; B.跨步电势差; C.接触电位差; D.跨步电位差。
参考答案:C
Two cars left the same town traveling in the same direction. Car A traveled 40 miles per hour and left at 3:20. Car B traveled 50 miles per hour and left at 4:40. At what time will car B catch up with car A ?()
A.10:00
B.9:00
C.8:40
D.7:20
E.6:10
属于法律的是()
A、煤炭法
B、煤矿安全监察条例
C、安全生产法
D、安全生产许可证条例