In these days of technological triumphs, it is well to remind ourselves from time to time that living mechanisms are often incomparably more efficient than their artificial imitations. There is no better illustration of this idea than the sonar system of bats. It is billions of times more efficient and more sensitive than the radars and sonars designed by man.
17. The author suggests that the sonar system of bats ____
A) was at the height of its perfection 50 million years ago
B) is better than man-made sonar because it has had 50 million years to be be refined
C) should have been discovered by man many years ago
D) is the same as it was 50 million years ago
注:B 选项体现一段结尾和二段开头,应该优选,含有关系词 because,although,not only...but also, as well as 的应该优选
18. Echo location in this article means the _____.
A) location of echoes
B) ability to determine where an echo comes from
C) scientific term for sound waves
D) ability to locate unseen objects by echoes
注:1.A 为干扰选项,过于表面化
2.B 项为等价选项所以为错误
To appreciate the precision of the bats echo location, we must first consider the degree of their reliance upon it. Thanks to sonar, an insect-eating bat can get along perfectly well without eyesight. This was brilliantly demonstrated by the Italian naturalist
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