单项选择题
A. chief officer B. second officer C. third officer D. carpenter
Echo sounder sends a（） (无线电信号)from the bottom of the sh...
单项选择题Echo sounder sends a（） (无线电信号)from the bottom of the ship to the seabed.
A. radio signal B. radio wave C. signal D. signal radio
Radar is of great help to ship in poor（）(能见度).A.visibil...
单项选择题Radar is of great help to ship in poor（）(能见度).
A.visibility B.VHF C.visible D.compass
Navigators use navigational aids, such as（）（罗经）.A.sexta...
单项选择题Navigators use navigational aids, such as（）（罗经）.
A.sextant B.binoculars C.compass D.loran
