单项选择题 The Address Resolution Protocol(ARP) is employed at ( ).Interface LayerB、Internetwork LayerC、Host-to-Host Transport LayerD、Application Layer

单项选择题 Virtual Private Networks(VPN) are networks deployed on a ( ) network infrastructure.areaD、wide area

单项选择题 You may keep the book ( ) you like.well asB、as long asC、as soon asD、as far as