闭锁式高频保护的通道一般选用()祸合方式,如果线路内部故障时(),保护也不会拒动。
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机动车必须装臵后反射器。挂车及车长大于()的机动车应安装侧反射器和侧标志灯。
A. 4 m
B. 3.5 m
C. 7 m
D. 6 m
My fingernails are so ____ that they break off before they get long enough to polish.
A. elastic
B. strong
C. fragile
D. steady
An efficient engine is____ of fuel.
A. economic
B. economize
C. economical
D. economy