Open Shortest Path First(OSPF)is a (8) routing algorithm that (9) work done on the OSI IS-IS intradomain routing protocol. This routing, as compared to distance-vector routing, requires (10) processing power. The Dijkstra algorithm is used to calculate (11) OSPF routing table updates only take place when necessary, (12) at regular intervals.

8（）

A．distance-vector

B．link-state

C．flow-based

D．selective flooding