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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

admin2009-04-23  57
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.
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 文章第一段由跟踪蓝鲸引出话题。第一、二段讲述了生物学家运用海军监听系统取得的研究成果。第三、四、五段介绍了地球科学家以及其他科学家也已经或正在利用军方的设备进行各自的研究。第六段讲述了声音在水中传播的原理。综上所述，本篇主要讲的是一种军事探测系统被民用科学界运用于科研的话题，故B正确。
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