The“urgent”priorityshouldbeusedformessages（）.
A. concerningtheSafetyofLifeatSea(SOLAS)
B. detailingimportantnavigationalwarnings
C. containinginformationconcerningthesafetyofamobileunitorperson
D. concerningon-scenecommunications
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The3-cmradarascomparedtoa10-cmradarwithsimilarspecificationswill（）.
A. givebetterrangeperformanceinrain，hail，etc
B. displaysmalltargetsinamassofdenseseaclutteratagreaterrange
C. havelessseareturninchoppyroughseas
D. displayamoremaplikepresentationforinshorenavigation
Thisarrangementis（）iftheelementsaredirectlyconnectedtooneanotherandthecontrolactiontakesplacewithouthumaninvolvement.
A. amanualclosedloop
B. amanualopenedloop
C. anautomaticclosedloop
D. anautomaticopenedloop
In（）thecontrolactionisindependenton(of)theoutput.
A. aclosedloopcontrolsystem
B. anopenloopcontrolsystem
C. aboilercontrolsystem
D. asteeringgearcontrolsystem
Theerrorinthemeasurementofthealtitudeofacelestialbody，causedbyrefraction，increasesasthe（）.
A. horizontalparallaxdecreases
B. observer'sheightabovesealevelincreases
C. humidityoftheatmospheredecreases
D. altitudeofthebodydecreases
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