单项选择题
Which Internet Protocol(IP) telephony element is best categorizedas a voice application component?（）
A.IP telephone
B.Voice gateway
C.Private branch exchange (PBX)
D.Advanced audio conferencing software
单项选择题 What feature does the Partner E-Learning Connection provide?（）
单项选择题 Which device is installed in user devices and makes wireless connections between them and a network?（）
单项选择题 Which Cisco product is a software component that blocks unwanted connections and provides other gateway security functions for small business?（）