单项选择题
A receiving host computes the checksum on a frame and determines that the frame is damaged.Theframe is then discarded.At which OSI layer did this happen？（）
A.session B.network C.physical D.data link E.transport
多项选择题 Which two benefits are provided by creating VLANs? （）
多项选择题 Which of the following are key characteristics of PPP (Choose three.)（）。
多项选择题 Whichthreeelementsmustbeusedwhenyouconfigurearouterinterfaceforvlantrunking？（）
