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單項選擇題

In modern fathometers the sonic or ultrasonic sound waves are produced electrically by means of a(n)（）.

A.transmitter
B.transducer
C.transceiver
D.amplifier

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單項選擇題

In mid-ocean，the characteristics of a wave are determined by three factors. What is NOT one of these factors?（）.

A.Effect of the moon's gravity
B.Fetch
C.Wind velocity
D.Length of time a wind has been blowing

單項選擇題

In a tropical cyclone，in the Northern Hemisphere，a vessel hove to with the wind shifting counterclockwise is（）.

A.ahead of the storm center
B.in the dangerous semicircle
C.in the navigable semicircle
D.directly in the approach path of the storm