砖应丁码成方垛，不得超高，距沟槽坑边不应小于（）防止坍塌。
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With regard to bridges and switches, which of the following statements are true?（）
A. Switches are primarily software based while bridges are hardware based.
Both bridges and switches forward Layer 2 broadcasts.
C. Bridges are frequently faster than switches.
D. Switches typically have a higher number of ports than bridges.
E. Bridges define broadcast domain while switches define collision domains.
F. Both bridges and switches make forwarding decisions based on Layer 2 addresses.
解编操作时，主控动车组转换为调车模式后，必须一次移动多少米以上方可停车？
党员因工作不负责任致使所管理的人员出走，对直接责任者和领导责任者，怎么处分？
交一交变频器把工频交流电整流为直流电，然后再由直流电逆变为所需频率的交流电。
A. 正确
B. 错误
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