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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

admin2022-06-23  28
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 part of 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 planned 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.
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 通读全文可知，文章开头用追踪蓝鲸的例子说明了水下跟踪的难度很高；接下来讲述了生物学家用美国海军的水下监听绝密设备追踪了蓝鲸43天；第三、四、五段讲述了冷战之后，美国海军开始与民间科学家分享其部分水下监听系统，地球科学家用这一系统监测深海火山的爆发，其他科学家提议用该系统追踪洋流、测量海洋和全球温度的变化；最后一段阐述了这一探测技术的原理。因此，文章主要是围绕“军事探测系统的民用化”展开论述的。故选B。
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