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單項選擇題

The operator of the ship’s radiotelephone，if the radiotelephone is carried voluntarily，must hold at least a（）.

A.Mate's license
B.Restricted radiotelephone operator permit
C.Second-class radio operator's license
D.Seaman's document

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單項選擇題

The operation of which aids to navigation may be suspended during war or national emergency（）.

A.Navigational satellites
B.Loran
C.Omega
D.Any of the above

單項選擇題

The loran lines drawn on navigation charts represent（）.

A.Ground waves
B.Skywaves
C.Either ground waves or skywaves interchangeably
D.An average between ground wave and skywave positions