物流是产生商流的物质基础，在发生次序的先后上商流是物流的先导。
参考答案：对
Astronauts in a spaceship have to _______weightless conditions _______are quite different from ______ on the earth. [ ]
A. do with; which; those
B. deal with; that; that
C. face; which; those
D. solve; where; what
在灾难系统的建设国际标准中，批量在线数据库镜像或日志传输属于哪一层（）
A.3
B.4
C.5
D.6
