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單項(xiàng)選擇題

Exchange of answer-backs acts a confirmation that the messages（）at the destination.

A.have received
B.have been received
C.are received
D.are being received

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單項(xiàng)選擇題

The beacon located on board aircraft is termed（）.

A.EPIRB
B.PLB
C.ELT
D.MCC

單項(xiàng)選擇題

（）is capable of finding any 406MHZ beacons no matter where they are.

A.Local User Terminal
B.Spacecraft
C.Local-mode coverage
D.Near polar orbiting satellites

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