正解:B
The administrative distance is used as a trust rating for route entries (B). It is a metric used by routers to select the best path when there are two or more different routes to the same destination from two different routing protocols. The lower the administrative distance value, the more trustworthy the source of the route. For example, a directly connected network has an administrative distance of 0 because it is the most trusted source of routing information. In contrast, routes learned from different routing protocols have higher administrative distances, reflecting their relative trustworthiness.