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

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

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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
(5) 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
( 10) electrical field strengths about 1,000 times greater than
those known to excite electroreceptors.
Having discovered the electroreceptors, researchers are
now investigating how anteaters utilize such a sophisticated
sensory system. In one behavioral experiment, researchers
(15) 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,
( 20) researchers 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
(25)to locate unseen prey suggests, according to the researchers,
that the anteaters were using their electroreceptors
to locate the nesting chambers.
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 The best answer is D. According to the passage, the electrorecepors in the snouts of spiny anteaters responds to extremely weak electrical fields. In lines 7-11, the author of the passage contrasts these electroreceptors with tactile receptors, stating that it takes field strengths “about 1,000 times greater than those known to excite electroreceptors” to excite the tactile receptors on an anteater’s snout. The passage does not contrast the two types of receptors with regard to the characteristics mentioned in choices A, B, C, and E.
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