单项选择题

The underwater listening system was originally designed______ .

A．to trace and locate enemy vessels
B．to monitor deep-sea volcanic eruptions
C．to study the movement of ocean currents
D．to replace the global radio communications network

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热门试题

单项选择题

Which of the following is true about the U. S. Navy underwater listening network

A．It is now partly accessible to civilian scientists.
B．It has been replaced by a more advanced system.
C．It became useless to the military after the cold war.
D．It is indispensable in protecting endangered species.

单项选择题

The deep-sea listening system makes use of______ .

A．the sophisticated technology of focusing sounds under water
B．the capability of sound to travel at high speed
C．the unique property of layers of ocean water in transmitting sound
D．low-frequency sounds traveling across different layers of water