题型:阅读理解 题类:常考题 难易度:普通
江苏省新草桥中学2019届高三上学期英语12月月考试卷
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 his 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. 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 (化石)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 ichthyosaur 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 Triassic 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 they died, but not a single Triassic specimen(标本) 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 Rothschild thinks happened. He suspects it was evolution in other animals that caused the change.
Whales that suffer the bends often do so because they have surfaced to escape a predator (捕食动物) such as a large shark. One of the features of Jurassic oceans was an abundance of large sharks and crocodiles, both of which were fond of ichthyosaur lunches. Triassic oceans, by contrast, were mercifully shark- and crocodile-free. In the Triassic, then, ichthyosaurs were top of the food chain. In the Jurassic and Cretaceous, they were prey(猎物) as well as predator—and often had to make a speedy exit as a result.
Health is the most important thing in the world.Nothing is more important than health.If one takes away our money, houses, cars, or even our clothes, we can still survive.{#blank#}1{#/blank#} That is why we always try to eat in a healthy way and exercise often.
How can we keep healthy? In order to eat healthily, I usually avoid eating food high in fat, like French fries or cookies, which are junk foods.{#blank#}2{#/blank#} Besides, I only eat a little meat.
{#blank#}3{#/blank#} Taking exercise every day helps us build a strong body.Regular exercise is an important part of keeping me healthy.
What's more, I think friends are important part of one's health.{#blank#}4{#/blank#} I always feel better when I am with friends than I am alone.When I am with my friends, I always laugh.Laughing is also an important part of health.It is good to stay with my friends.
By eating properly and exercising regularly, I can keep my body at a proper weight and keep healthy.By spending time with my friends, I can keep my mind as well as my body happy.These things sound easy to do, but not many people can manage them.{#blank#}5{#/blank#}
A.Many studies show that people with a narrow range of social contacts often get sick. B.I think a strong will is necessary if we want to keep healthy. C.On the other hand, doing exercise is very important. D.There are some people who like staying alone, but they keep healthy. E.Some people appear fat because they often eat too much. F.But if our health is taken away, it is certain that we will surely die. G.I eat a lot of vegetables and fresh fruit which are full of vitamins. |
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