單項選擇題

According to the following statement， can you tell me which term is described？（）
It is the air return for an air conditioned system. In most buildings， the area above a drop ceiling orunder a raised floor is used as the air return （source of air） for the air conditioning. Those drop
ceiling and raised floors are also where wire is often installed. If wire and cable is installed in a dropceiling or raised floor， it is out of sight. If that cable were burning， it would give off toxic fumes.These would be fed to the rest of the building by the air conditioner. As a result， people could beinjured even though they are a long way from the fire.

A.DAS area
B.plenum area
C.extended area
D.RF special area


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2.單項選擇題What will cause wireless voice devices to perform poorly？（）

A.average signal strength that is greater than -67 dBi
B.cell overlap of 15 to 20 percent
C.uneven wireless coverage
D.absence of coverage holes

3.單項選擇題What does a Cisco Unified Wireless IP Phone 7921G deployment require（）？

A.more access points than a data network
B.fewer access points than a data network
C.less SNR than a data network
D.specific relative access point placement

5.多項選擇題Which two methods can be used to prevent or reduce RFI from colocated directional antennas（）

A.Alternate polarization between colocated antennas
B.Cross-polarize antennas between endpoints
C.Install an RF-shielded box around the antennas
D.Increase the distance between the antennas