Earth scientists announced at a news conference recently that they had used the system for closely monitoring a deep-sea volcanic eruption for the first time and that they plan similar studies.
Other scientists have proposed to use the network for tracking ocean currents and measuring changes in ocean and global temperatures.
The speed of sound in water is roughly one mile a secondslower than through land but faster than through air. What is most important, different layers of ocean water can act as channels for sounds, focusing them in the same way a stethoscope does when it carries faint noises from a patients chest to a doctors ear. This focusing is the main reason that even relatively weak sounds in the ocean, especially low-frequency ones, can often travel thousands of miles.
31. The passage is chiefly about ________.
A) an effort to protect an endangered marine species
B) the civilian use of a military detection system
C) the exposure of a U.S. Navy top-secret weapon
D) a new way to look into the behavior of blue whales(B)
32. 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(A)
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