问题
单项选择题
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 router attached to the destination network. A router receives a (4)from a network and passes it to another network. A router is usually attached to several networks. When it receives a packet, to which network should it pass the packet? The decision is based on optimization: Which of the available (5)is the optimum pathway?
空白（4）处应选择（）
A.destination
B.resource
C.packet
D.source
答案
参考答案：A
解析：
参考译文因特网是由路由器连接的网络的组合。当一个数据报从源出发到达目标时，它也许经过了许多路由器，直到它到达连接目标网络的路由器。路由器从网络接收一个分组，把它传递到另外一个网络。一个路由器通常连接多个网络。当收到一个分组时，路由器应该把它传递给哪个网络呢？这个决策是最优化的，取决于哪条通路是最优通路？