正解:A
Enhanced Interior Gateway Routing Protocol (EIGRP) uses bandwidth and delay as its primary metrics to determine the best path for routing traffic. EIGRP is an advanced distance-vector routing protocol, which is proprietary to Cisco systems, making it highly efficient in a variety of network designs. It can also utilize load, reliability, and maximum transmission unit (MTU) as additional metrics, but bandwidth and delay are the primary considerations in its composite metric calculation. Other protocols listed, such as RIP, OSPF, and BGP, use different metrics like hop count (RIP) and cost based on link state (OSPF), or make decisions based on path attributes and policy (BGP).