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
点击查看答案
相关考题
-
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 -
单项选择题
Navigators use navigational aids, such as（）（罗经）.
A.sextant
B.binoculars
C.compass
D.loran -
单项选择题
（）（电罗经）can tell us true north.
A.VHF
B.Radar
C.Chart
D.Gyro-compass
