DVOR设备告警自动换机时间不得超过()。
A.15秒
B.10秒
C.5秒
D.30秒
参考答案:B
____ we get on well with a number of people , we are usually friends with only a very few.
A.As
B.Once
C.Before
D.While
非电导爆管的技术特性,其爆速为()每米药量为16-20g。
A.1600~1700m/s
B.1700~1800m/s
C.1900~2000m/s