单项选择题 A technician needs to add network capacity. However, when plugging a second switch into the first switch, there is no link light. Which of the following is the cause of this situation?（）

单项选择题 Which of the following wiring distribution components should be chosen to provide level integrateddiagnostic capabilities?（）

单项选择题 A demarcation point is usually installed and managed by which of the following providers?（）