An expanding company is deploying leased lines between its main site and two remote sites. The bandwidth of the leased lines is 128kb/s each， terminated on different serial interfaces on the main router. These links are used for combined VOIP and data traffic. The network administrator has implemented a VOIP solution to reduce costs， and has therefore reserved sufficient bandwidth in a low latency queue on each interface for the VOIP traffic. Users now complain about bad voice quality although no drops are observed in the low latency queue. What action will likely fix this problem？（）

A.mark VOIP traffic with IP precedence 6 and configure only ’fair-queue’ on the links
B.configure the scheduler allocate 3000 1000 command to allow the QoS code to have enough CPU cycles
C.enable class-based traffic shaping on the VoIP traffic class
D.enable Layer 2 fragmentation and interleaving on the links
E.enable Frame Relay on the links and send voice and data on different Frame Relay PVCs