|
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 Lazzaro Spallanzani. He caught some bats in a bell tower, blinded them and released them outdoors. Four of these blind bats were recaptured after they had found their ways back to the bell tower, and on examining their stomachs contents, Spallanxani found that they had been able to capture and eat flying insects. We know from experiments that bats easily find insects in the dark of night, even when the insects make no sound that can be heard by human ears. A bat will catch hundreds of softbodied silent flying insects in a single hour. It will even detect and chase pebbles tossed the deficiencies of man-made sonar B) the dependence of man upon animals C) that we are living in a machine age D) that the sonar system of bats is remarkable 注：写作目的题型，写作目的=写作动机+文章主题，看文章主题第一句话 20. The following is the main point of the article:____ A) A bat will catch hundreds of insects in a single hour. B) There is a perfection in nature which sometimes can not be matched by mans creative efforts. | 
