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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 into the air. Questions 31 to 35 are based on the following passage: 31. When a consumer finds that his purchase has a fault in it, the first thing he should do is to ________ A) complain personally to the manager B) threaten to take the matter to court C) write a firm letter of complaint to the store of purchase D) show some written proof of the purchase to the store 32. If a consumer wants a quick settlement of his problem, its better to complain to ________. | 
