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

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

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B．It has been replaced by a more advanced system.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.