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.
According to the passage, which of the following is a characteristic that distinguishes electroreceptors from tactile receptors?
选项 A、The manner in which electroreceptors respond to electrical stimuli.
B、The tendency of electroreceptors to be found in clusters.
C、The unusual locations in which electroreceptors are found in most species.
D、The amount of electrical stimulation required to excite electroreceptors.
E、The amount of nervous activity transmitted to the brain by electroreceptors when they are excited.
答案D
解析 电接收器和触觉接收器的不同体现在：A．对电刺激反应方式。B．成群分布。C．不寻常位置。E．传送神经活动的数量。上述四点原文均未提。D．正确。引起兴奋的电刺激量。原文L13—17，触觉接收器起反应的电场强度比电接收器要高1000倍。
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