押江苏卷28—31题-阅读理解C篇说明文-备战2021年高考英语临考题号押题

押江苏卷第28—31题 阅读理解C篇说明文 Passage 1 If a diver surfaces too quickly, he may suffer the bends. Nitrogen (氮) dissolved (溶解) in his blood is suddenly liberated by the reduction of pressure. The consequence, if the bubbles (气泡) accumulate in a joint, is sharp pain and a bent body — thus the name. If the bubbles form in his lungs or brain, the consequence can be death. Other air-breathing animals also suffer this decompression (减压) sickness if they surface too fast: whales, for example. And so, long ago, did ichthyosaurs (鱼龙). That these ancient sea-animals got the bends can be seen from their bones. If bubbles of nitrogen form inside the bone they can cut off its blood supply. This kills the cells in the bone, and consequently weakens it, sometimes to the point of collapse. Fossil bones that have caved in on themselves are thus a sign that the animal once had the bends.  Bruce Rothschild of the University of Kansas knew all this when he began a study of ichthyosaurs bones to find out how widespread the problem was in the past. What he particularly wanted to investigate was how ichthyosaurs adapted to the problem of decompression over the 150 million years. To this end, he and his colleagues traveled the world’s natural-history museums, looking at hundreds of ichthyosaurs from the Trassic period and from the later Jurassic and Cretaceous periods. When he started, he assumed that signs of the bends would be rarer in younger fossils, reflecting their gradual evolution of measures to deal with decompression. Instead, he was astonished to discover the opposite. More than 15% of Jurassic and Cretaceous ichthyosaurs had suffered the bends before the died, but not a single Trassic specimen showed evidence of that sort of injury. If ichthyosaurs did evolve an anti-decompression means, they clearly did so quickly — and, most strangely, they lost it afterwards. But that is not what Dr Rothchild thinks happened. He suspects it was evolution in other animals that caused the change. Wh