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举一反三
【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
【多选题】焊缝布置的要求有______等。
A.
焊缝应尽可能分散
B.
焊缝的位置应尽可能对称分布，以抵消焊接变形
C.
焊缝应尽可能避开最大应力和应力集中的位置
D.
焊缝应尽量避开机械加工表面，以防止破坏已加工面