在机房环境的设计中,按照有关国家标准,地板载重量必须大于 (74) kg/m2,表面电阻应大于 (75) MΩ。
A.300
B.400
C.500
D.600
参考答案:C
为了改善分离效果,重力式油水分离器宜采用()。
A.高速离心式水泵
B.低速往复泵
C.高速齿轮泵
D.喷射泵
The height of a VHF radio antenna is more important than the power output wattage of the radio because().
A.VHF communications are basically line of sight
B.the air is more dense the higher you go
C.salt water is a poor conductor of sound
D.sea water absorbs the radiated energy