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  3. It is hard to track the blue whale, the ocean’s largest creature, which has almost been killed off by commercial whaling and is

It is hard to track the blue whale, the ocean’s largest creature, which has almost been killed off by commercial whaling and is

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问题     It is hard to track the blue whale, the ocean’s largest creature, which has almost been killed off by commercial whaling and is now listed as an endangered species. Attaching radio devices to it is difficult, and visual sightings are too unreliable to give real insight into its behavior.
    So biologists were delighted early this year when, with the help of the Navy, they were able to track a particular blue whale for 43 days, monitoring its sounds. This was possible because of the Navy’s formerly top-secret system of underwater listening devices spanning the oceans.
    Tracking whales is but one example of an exciting new world just opening to civilian scientists after the cold war as the Navy starts to share and partly uncover its global network of underwater listening system built over the decades to track the ships of potential enemies.
    Earth scientists announced at a news conference recently that they had used the system for closely monitoring a deep-sea volcanic eruption (爆发) 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 second—slower 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 (听诊器) does when it carries faint noises from a patient’s chest to a doctor’s 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. (283 words)
The passage is chiefly about______.
选项 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
答案B
解析 本题属于主旨归纳题。前两段主要讲科学家用水下监听系统跟踪蓝鲸，而这只是其用途的一个例子，“Tacking whales is but one example”，从而我们可以推知深海监听系统有更为重要的用途：如深海监听系统的民用化，“opening to civilian scientists”。第四段指出军事监测系统运用于监测深海的火山爆发，“closely monitoring a deep-sea volcanic eruption”；第五段指出其他科学家建议用这个系统跟踪海洋气流，测量海洋变化以及全球气温变化，“for tracking ocean currents and measuring changes in ocean and global temperatures”。所以本文的主要脉络是围绕军事监测系统的民用化展开的，故选B。
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