WhatisoneofthereasonsthatcustomQoSACLsarerecommendedoverautomaticQoSwhen configuringportsonaCatalyst6500forusewithIPphones?()

A.79xxIPphonesdonotautomaticallymarkvoicepacketswithnon-zeroDSCPvalues.

B.79xxIPphonesdonotmarkprotocolpacketssuchasDHCP，DNS，orTFTPwithnon-zero DSCPvalues.

C.79xxIPphonesdonotmarkvoicepacketswithoptimalDSCPvalues.

D.79xxIPphonesuseacustomprotocoltocommunicateCDPinformationtotheswitch.