单项选择题
（）sends a radio signal from the bottom of the ship to the sea-bed,from which it is reflected.
A.The marine sextant
B.The chronometer
C.The echo sounder
D.The radar
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相关考题
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单项选择题
（）is the navigational timekeeper of the vessel.
A.The marine sextant
B.The chronometer
C.The magnetic compass
D.The gyrocompass -
单项选择题
（）is used for measuring horizontal and vertical angles.
A.The marine sextant
B.Thechronometer
C.The magnetic compass
D.The gyrocompass -
单项选择题
（）means rudder to be held in the force and aft angles.
A.Steady
B.Meet her
C.Midships
D.Stop engines
