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  3. It is hard to track the blue whale, the ocean’s largest creature, which has a

It is hard to track the blue whale, the ocean’s largest creature, which has a

游客2025-01-04  42
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 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 does when it carries faint noise 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 Iow-frequency ones, can often travel thousands of miles. [br] 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 本文首先以“tracking whales”为例说明“the Navy’s formerly top-secret system of underwater listening devices”对民用研究的用途，然后又讲到其他科学家利用这一系统来进行科学研究的例子，这一切都说明文章的主要内容是“the civilian use of a military detection system”，所以，[B]是正确答案。从第三段中的“tracking whales is but one example of an exciting new world just opening to civilian scientists…”可以看出“an effort to protect an endangered marine species”，并不是文章的主要内容，所以，[A]不符合题意。本文只在第三段中涉及了这样一个事实“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”，这只是一个细节，根本就谈不上是文章主要内容。故[C]不合题意。利用海底无线电网络系统对蓝鲸的行为进行观测只是这一系统的一个应用方面，也谈不上是文章的主旨，[D]不是正确答案。
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