组成房屋的构件中，下列既属承重构件又属围护构件的为（）。

A.墙体、屋顶

B.楼板、基础

C.屋顶、基础

D.门窗、墙体

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.

11（）

A．routes

B．road

C．distance

D．cost