Bluetooth is a universal radio interface in the (71) frequency hand that enables portable electronic devices to connect and communicate wirelessly via short-range, ad hoc networks. Each unit can simultaneously communicate with up to (72) other units per piconet. Moreover, each unit can simultaneously (73) to several piconets. Eliminates the need for wires, cables and connectors for and between cordless or mobile phones, modems, headsets, PDAs, Computers, printers, projectors, local area networks, and so on, and paves the way for new and completely different devices and applications. Technology Characteristics (74) symbol rate exploits maximum available (75) bandwidth。

A．server

B．firewall

C．clinet

D．router

两种不同金属材料，把其中一端对焊起来，另两端与电压表相连，当两端之间有温度差时，就会产生（）电动势，这种现象称为赛贝克效应，这种导体的组合称为（）。