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1. In the following essay，each blank has fourchoices.Choose the best answer and write down on thean，swer sheet.
Microwave communication uses(1)frequency radio waves that travel instraighdine sthroughthe air.Because the waves cannot(2)with the curvature of the earth，they can be (3)onlyover short distance.Thus，microwave is a good(4)for sending data between bulldingsin a city or on a large college campus.For longer distances，the waves must berelayed by means of“dishes”or (5).These can be installed on towers，highbuildings，and mountain tops.
(1)A.high
B.10w
C.1ong
D.short
(2)A.reflex
B.distort
C.bend
D.absorb
(3)A.transmitted
B.transformed
C.converted
D.delivered
(4)A.material
B.equipment
C.medium
D.channel
(5)A.repeaters
B.radars
C.telephones
D.antennas
2. (1)In the strength of the carrier signal is varied to represent binary1 or 0.
(2)is a system that can map a name to an address and conversely an addressto an name.
(3)is a three-way handshaking authentication protocol that it's packets areencapsulated inthe point-to-point protocol
(4)is an approach that enables an ATM Switch to behave like a LAN switch.
(5)is an guided media which is made of glass or plastic and trans mitssignals in the form of light.
(1)A.ASK
B.PSK
C.FSK
D.FDM
(2)A.NAT
B.NCP
C.DDN
D.DNS
(3)A.PPP
B.PAP
C.CHAP
D.LCP
(4)A.VLAN
B.LANE
C.VPN
D.IPOA
(5)A.Coaxial cable
B.Optical fiber
C.Unshielded Twisted-pair Cable
D.Shielded Twisted-pair Cable
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