QoSreferstotheabilityofanetworktoprovideimprovedservice,overvariousunderlyingtechnologies,toselectnetworktraffic.WhichtwotraitsareinherenttoQoS?()

A.referencetonetworkabilitytoprovideimprovedservicetoallnetworktraffic

B.reductionindelay，jitter，andpacketloss

C.equalhandlingofallpackets

D.supportforreal-timeapplications

E.best-effortactions