单项选择题
Which statement about VPLS is true？（）
A.All CE devices emulate a bridge B.All provider devices emulate a bridge C.Hierarchical VPLS reduces signaling overhead D.Each PE device emulates a bridge E.Each CE device emulates a bridge
单项选择题 Whatmethodofstreaminglivevideoistheleasttaxingonbandwidthinalargeenterpriseenvironment？（）
单项选择题 WhichstatementisFALSEconcerningConcatenation？（）
单项选择题 Inopticaltransmissionsystems，chirpedlasersareusedforthepurposeof：（）.
