指出句子中的错误并改正。

人们一走进教学楼就会看到，所有关于澳门历史的图片和宣传画都被挂在走廊两边的墙壁上。

One of the most widely used routing protocols in IP networks is the Routing Information Protocol (RIP). RIP is the canonical example of a routing protocol built on the (71) algorithm. Routingprotocols in internetworks differ slightly from the idealized graph model. In an internetwork, the goal ofthe routers to forward (72) to various networks.
Routers running RIP send their advertisement abOLit cost every (73) seconds. A router also sends an up date message whenever an update from another router causes it to change its routing table.
Routing protocols use different techniques for assigning (74) to individual networks. Further, each routing protocol forms a metric aggregation in a different way. RIP takes the simplestapproach, with all link costs being equal (75) . Thus it always tries to find the minimum hop route. Valid distances are 1 through 15. This also limits RIP to running on fairly small networks.

A．data frames
B．segments
C．packets
D．messages