Themakingofglassisaveryoldindustry—atleast4500yearsold.Glasshasmanyextraordinaryqualitiesanditisfrequentlybeingusedinnewways.Oneofthemostinterestingnewusesforglassisintelephonecommunication.Scientistshavedevelopedglassfibersasthinashumanhairwhicharedesignedtocarrylightsignals.Whenthelightreachestheotherenditisfirstchangedintoelectricalsignalswhichareinturnconverted(转变)intosoundmessages.Calledlightwavecommunication，thenewsystemwasusedsuccessfullyinanexperimentinChicagoin1977.Duringtheexperimenttwoglassfiberswereabletocarry672conversationsatthesametime.Thelightwavecablecontaining144glassfibershasthecapacity(容量)tocarry50000conversationsatthesametime.Thelightwavecommunicationsystemhastwoimportantadvantages.Firsttheglassfibercablesaresmallerandweighlessthancopper(铜)cables;secondtheycostless.

1.Oneoftheextraordinaryqualitiesofglassisthatitcancarry_______.

A.anysignal B.lightsignals

C.soundsignals D.electricalsignals

2.Beforeyoucanhearamessageonthetelephoneusingthenewsystem_______.

A.thelightsignalshavetobechangedintoelectricalsound

B.neitherthelightnortheelectricalsignalshavetobechangedinanyway

C.lightmustfirstbechangedintoelectricalsignalsandthenintosound

D.electricalsignalsmustfirstbechangedintolightsignalsandthenintosound

3.Accordingtothepassagethenewtelephonecommunicationsystem_______.

A.wasputonexperimentin1977

B.hadbeenputintoactualuseby1977

C.hadbeenrepeatedlyexperimentedbefore1977

D.wasfirstputintoactualusein1977

4.Fromthepassageyoucantellthatpeoplepreferglassfibercablestocoppercablesbecause_______.

A.glassfiberiseasiertomake

B.glassfiberislessexpensive

C.glassfiberismoreuptodate

D.glassfiberdeliversmessagesdirectly

5.Whichofthefollowingstatementsbestexpressesthemainideaofthepassage?

A.Lightsignalshavechangedtheuseofglassinindustry.

B.Glassfibershavereducedthecostoftel