正解:C
The preferred Quality of Service (QoS) marking for delay-sensitive real-time protocols, such as the Real-Time Protocol (RTP), is Expedited Forwarding (EF). EF is a per-hop behavior (PHB) that ensures low loss, low latency, and low jitter for critical traffic, such as voice and video. It is typically marked with a DSCP value of
46, which gives it the highest priority in traffic forwardingdecisions on the network. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) training materials provide an in-depth understanding of QoS mechanisms and their application in service provider networks