软件危机出现于20世纪60年代末，为了解决软件危机，人们提出了 【3】 的原理来设计软件，这就是软件工程诞生的基础。
参考答案：【3】软件工程学
An internet is a combination of networks connected by （1）. When a datagram goes from a source to a （2）, it will probably pass many （3） until it reaches the routerattached to the destination network. A router receives a （4）from a network and passes it toanother network. A router is usually attached to several networks. When it receives a packet, towhich network should it pass the packet The decision is based on optimization: Which of theavailable（5） is the optimum pathway
（5）是（）
A.pathways
B.routers
C.diagrams
D.calls
发动机从出厂服役到退役报废的总工作时数，叫发动机的（）。
