单项选择题 Which of the following devices is used to connect a WAN to a LAN?（）

单项选择题 A network administrator has been receiving work orders about poor voice quality crossing a branch T1. The cause is determined to be users running high bandwidth file sharing applications across the T1 sending large packets delaying the smaller voice streams. Which of the following would improve voice quality?（）

单项选择题 Which of the following is resistant to crosstalk?（）