B) modern machines are inefficient
C) living mechanisms are often more efficient than man -made machines
D) artificial imitations are always less efficient than living mechanisms
注:1.第一段 illustration 等同 example
2.D选项的always与文章中的often含义是不同的。
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
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