The integrated logistics activities, equipment and information network and so on, is called ()
A. logistics integration
B. logistics industry
C. logistics center
D. logistics park
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拱桥中从拱顶截面下缘至相邻两拱脚截面下缘最低点连线的垂直距离为()。
A. 净矢高
B. 计算矢高
C. 标准矢高
D. 基准矢高
如果原问题的某个变量无约束,则对偶问题中对应的约束条件应为()