The metric assigned to each network depends on the type of protocol. Some simple protocol, like RIP, treats each network as equals. The ______ of passing through each network is the same; it is one ______ count. So if a packet passes through 10 network to reach the destination, the total cost is 10 hop counts. Other protocols, such as OSPF, allow the administrator to assign a cost for passing through a network based on the type of service required.A ______ through a network can have different costs (metrics). For example, if maximum ______ is the desired type of service, a satellite link has a lower metric than a fiber-optic line. On the other hand, if minimum ______ is the desired type of service, a fiber-optic line has a lower metric than a satellite line. OSPF allow each router to have several routing table based on the required type of service.

A．flow
B．hop
C．process
D．route

电气短路故障产生的原因主要为（）

A、电气绝缘击穿

B、违章带电作业和误操作

C、机械损伤

D、漏电扩大造成

E、设备超载运行