多项选择题 A single 802.11g access point has been configured and installed in the center of a square office. A few wireless users are experiencing slow performance and drops while most users are operating at peak efficiency. What are three likely causes of this problem?（）

多项选择题 What are two security appliances that can be installed in a network?（）

多项选择题 Which of the following describes the roles of devices in a WAN?（）