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 underwater listening system was originally designed______.

选项 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

答案A

解析 本题属于细节理解题。根据题干的“originally designed”定位第三段尾句,并可替换“built over the decades”。接下来的动词不定式表示建造的目的:跟踪潜在敌人的船只,“to track the ships of potential enemies”。选项A“跟踪并定位敌人船只”,明确无误地表述了这一观点。此题的关键在于“vessel”这个词的正确理解,在现在这个语境下,它就是ship的同义词。第四段一开始说:“Earth scientists have announced…that they had used the system closely monitoring a deep—sea volcanic eruption”“地球科学家在新闻发布会上发布:他们已经使用该系统近距离监测深海火山爆发……”。可见,B并不是最初的军用用途。第五段谈到: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,这也是民用,不是系统的军用目的,故C也排除。D的说法文中没有暗示。
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