单项选择题
In the 7-layer OSI model, which layer switching will take place?（）
A.Layer two B.Layer four C.Layer one D.Layer three
单项选择题 In which area of the campus LAN are the user computers attached to the network?（）
多项选择题 Which three are current small business needs for technology investments? （）
单项选择题 Which device is installed in user devices and makes wireless connections between them and a network?（）
