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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.
102. Which of the following can be inferred about the
experiment described in the first paragraph?
(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 electro receptors..
(E) Researchers tested small areas of the anteater’s snout
in order to ensure that only electroreceptors were
responding to the stimulus.
请 问 E为 什 么 不 对 呢 ？ 应 该 如 何 排 除 ？ 多 谢
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发表于 2005-10-27 03:40:00
