Networks can be interconnected by different devices in the physical layer networks can be connected by _(1)_ or hubs .which just move the bits from one network to an identical network. One layer up we find bridges and switches which operate at data link layer. They can accept _(2)_ examine the MAC address and forward the frames to a different network while doing minor protocol translation in the process in me network layer ,we have routers that can connect two networks, If two networks have _(3)_ network layer, the router may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections Finally, in the application layer, application gateways translate message _(4)_ .As an example, gateways between Internet e-mail and X.400 e-mail must _(5)_ the e-mail message and change various header fields.
　　（1）A．reapers
　　B．relays
　　C．packages
　　D．modems
　　（2）A．frimes
　　B．packets
　　C．packages
　　D．cells
　　（3）A．special
　　B．dependent
　　C．similar
　　D．dissimilar
　　（4）A．syntax
　　B．semantics
　　C．language
　　D．format
　　（5）A．analyze
　　B．parse
　　C．delete
　　D．create
　　答案：A A D B B

      　The purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable _ (1) _ of the technical requirements for the software product.
　　During the requirements definition phase, the requirements definition team uses an iterative process to expand a broad statement of the system requirements into a complete and detailed specification of each function..that the software must perform and each _ (2) _ that it must meet. The starting point is usually a set of high level requirements from the _ (3) _ that describe the project or problem.
　　In either case, the requirement definition team formulates an overall concept for the system and then defines _ (4) _ showing how the system will be operated publishes the system and operations concept document and conducts a system concept review (SCR).
　　Following the SCR, the team derives _ (5) _ requirements for the system from the high level requirements and the system and operations concept. Using structured or object-oriented analysis. the team specifies the software functions and algorithms needed to satisfy each detailed requirement.
　　（1）A．function　　　B．definition　　　C．specification　　D．statement
　　（2）A．criterion　　 B．standard　　　　C．model　　　　　　D．system
　　（3）A．producer　　　B．customer　　　　C．programmer　　　 D．analyser
　　（4）A．rules　　　　 B．principles　　　C．scenarios　　　　D．scenes
　　（5）A．detailed　　　B．outlined　　　　C．total　　　　　　D．complete

       在分支-限界算法设计策略中，通常采用_(1)_搜索问题的解空间。
　　(1)A．深度优先
　　B．愣扔畔取
　　C．自底向上
　　D．拓扑序列
　　●在下列算法设计方法中，_(2)_在求解问题的过程中并不从整体最优上加以考虑，而是做出在当前看来是最好的选择。利用该设计方法可以解决_(3)_问题。