In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet.
Open Shortest Path First(OSPF) is a (66) routing algorithm that (67) work done on the OSI IS-IS intradomain routing protocol. This routing, as compared to distance-vector routing, requires (68) processing power. The Dijkstra algorithm is used to calculate (69) OSPF routing table updates only take place when necessary, (70) at regular intervals.

A．derived from

B．deviated from

C．was derived from

D．was deviated from

（）是公安机关的根本建设，是一项长期的、具有战略意义的大事。

A.公安业务建设

B.公安文化建设

C.公安队伍正规化建设

D.公安装备建设