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【单选题】Subways are underground trains, which usually operate 24 hours a day. They are found in larger cities and usually run between the suburbs and the downtown area. Maps and schedules are available from t...
A.
within downtown areas
B.
away from city centers
C.
in or outside big modern cities
D.
between suburbs and city centers
【单选题】数控机床上电启动,电路在接通的瞬间,熔断器发生熔断故障,请问处理的方法有( )。
A.
更换熔断器的熔体和查找负载侧是否短路
B.
检查电网电压，增加稳压器
C.
检查电动机转子线圈是否短路
D.
交流接触器安装灭弧装置