物流管理信息系统开发的周期,以下顺序正确的是:( ) A. 系统规划阶段→系统实施阶段→系统设计阶段→系统分析阶段→系统运行阶段 B. 系统分析阶段→系统规划阶段→系统设计阶段→系统实施阶段→系统运行阶段 C. 系统规划阶段→系统分析阶段→系统设计阶段→系统实施阶段→系统运行阶段 D. 系统规划阶段→系统分析阶段→系统设计阶段→系统运行阶段→系统实施阶段
【单选题】Viruses cause many human infections such as hepatitis, encephalitis, and the “ common cold. ” Which one of the following is a common trait of all these viruses?
A.
They are small, circular DNA molecules that enter bacteria and replicate outside the host genome.
B.
Upon infecting eukaryotic cells, they are called phages.
C.
All the common cold viruses contain both DNA and RNA genomes.
D.
In order to reproduce, they must use the infected cell ’ s DNA, RNA, and protein-synthesizing machinery.
E.
Upon becoming infectious, they are called plasmids.