2. 外语
  3. Australian researchers have discovered electroreceptors(sensory organs designed to respond to electrical fields)clustered at the

Australian researchers have discovered electroreceptors(sensory organs designed to respond to electrical fields)clustered at the

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问题     Australian researchers have discovered electroreceptors(sensory organs designed to respond to electrical fields)clustered at the tip of the spiny anteater’ s snout. The researchers made this discovery by exposing small areas of the snout to extremely weak electrical fields and recording the transmission of resulting nervous activity to the brain. While it is true that tactile receptors, another kind of sensory organ on the anteater’ s snout, can also respond to electrical stimuli, such receptors do so only in response to electrical field strengths about 1, 000 times greater than those known to excite electro-receptors.
    Having discovered the electroreceptors, researchers are now investigating how anteaters utilize such a sophisticated sensory system. In one behavioral experiment, researchers successfully trained an anteater to distinguish between two troughs of water, one with a weak electrical field and the other with none. Such evidence is consistent with researchers’ hypothesis that anteaters use electroreceptors to detect electrical signals given off by prey; however, re- searchers as yet have been unable to detect electrical signals emanating from termite mounds, where the favorite food of anteaters live. Still, researchers have observed anteaters breaking into a nest of ants at an oblique angle and quickly locating nesting chambers. This ability quickly to locate unseen prey suggests, according to the researchers, that the anteaters were using their electrorecep- tors to locate the nesting chambers.
Which of the following can be inferred about the experiment described in the first paragraph?
选项 A、Researchers had difficulty verifying the existence of electroreceptors in the anteater because electroreceptors respond to such a narrow range of electrical field strengths.
B、Researchers found that the level of nervous activity in the anteater ’ s brain increased dramatically as the strength of the electrical stimulus was increased.
C、Researchers found that some areas of the anteater’s snout were not sensitive to a weak electrical stimulus.
D、Researchers found that the anteater’s tactile receptors were more easily excited by a strong electrical stimulus than were the electroreceptors.
E、Researchers tested small areas of the anteater’ s snout in order to ensure that only electroreceptors were responding to the stimulus.
答案C
解析 关于第一段的实验：A．很难验证电接收器存在。说反了，原文已经验证。B．神经活动水平随电流增高而增高。未提C．正确。发现嘴的一部分对弱电流刺激不敏感。原文L13—17，触觉接收器就不能感应弱电流。D．在强电流下，触觉接收器比电接收器更易激发。原文无此比较。E．只有电接收器对电流起反应。不合原文。
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