局内光缆的光缆护层结构应选择()。
A.PE内护层+防潮铠装层+PE外护层
B.防潮层+PE外护层
C.防潮层+PE内护层+钢丝铠装层+PE外护层
D.非延燃材料外护层
参考答案:D
Students are encouraged to _____ the design competition for robots at the university. [ ]
A. take part
B. operate
C. join to
D. participate in
电嘴的温度低于自洁温度,将导致().
A.击穿电压减小,混合气可能早燃
B.击穿电压增加,产生积炭,电火花强度减弱
C.击穿电压减小,电火花强度增加
D.击穿电压增加,电火花强度增大