题目内容
Sharks Perform a Service for Earth’s Waters It is hard to get people to think of sharks as anything but a deadly enemy. They are thought to (51) people frequently. But these fish perform a (52) service for earth’s waters and for human beings. Yet business and sport fishing are threatening their (53) . Some sharks are at risk of disappearing from (54) . Warm weather may influence both fish and shark activity. Many fish swim near coastal areas (55) their warm waters. Experts say sharks may follow the fish into the same areas, (56) people also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a person (57) a sea animal, such as a seal or sea lion. That is why people should not swim in the ocean when the sun goes down or comes up. Those are the (58) when sharks are looking for food. Experts also say that bright colors and shiny jewelry may cause sharks to attack. A shark has an extremely good sense of smell. It can find small amounts of substances in water, such as blood, body liquids and (59) produced by animals. These powerful (60) help sharks fred their food. Sharks eat fish, any (61) sharks, and plants that live in the ocean. Medical researchers want to learn more about the shark’s body defense, and immune (62) against disease. Researchers know that sharks (63) quickly from injuries. They study the shark in hopes of finding a way to fight human disease. Sharks are important for the world’s (64) . They eat injured and diseased fish. Their hunting activities mean that the numbers of other fish in ocean waters do not become too (65) . This protects the plants and other forms of life that exist in the oceans.
查看答案
搜索结果不匹配？点我反馈
更多问题
A over the past 50 years B beneath the earth surface C by more than 50 percent D for more than four decades E as a raw material F for families When manufacturing many products, people commonly use natural gas______.
患者，女，12岁，发现左下腹部有一肿物入院。肛查肿物如手拳大小，囊实性，B超检查少量腹水。 本例的预后，估计5年生存率为
某中学生，16岁，经骨髓穿刺检查诊断为“急性淋巴细胞白血病”，给以常规治疗，症状无缓解。医生告诉家长，此病目前尚无理想的治疗方法，医院正在尝试使用一种疗效不肯定、有一定风险的药物。其家长表示愿意做这种试验性治疗。但没有履行书面承诺手续。治疗2天后，病人病重，抢救无效后死亡。此后，家属否认曾同意这种治疗方案，称是“拿病人做试验”，要追究医生责任，于是造成医疗纠纷。 就本案分析，医生做出选择的伦理依据是
The Best Way to Reduce Your Weight You hear this: "No wonder you are fat. All you ever do is eating." You feel sad: "I skip my breakfast and supper. I run every morning and evening. What else can I do" Basically you can do nothing. Your genes, not your life habits, determine your weight and your body constantly tries to maintain it. Albert Stunkard of the University of Pennsylvania found from experiments that, "80 percent of the children of two obese parents become obese, as compared with no more than 14 percent of the offspring of two parents of normal weight." How can obese people become normal or even thin through dieting Well, dieting can be effective, but the health costs are tremendous. Jules Hirsch, a research physician at Rockefeller University, did a study of eight fat people. They were given a liquid formula providing 600 calories a day. After more than 10 weeks, the subjects lost 45kg on average. But after leaving the hospital, they all regained. The results were surprising by metabolic measurement, fat people who lost large amounts of weight seemed like they were starving. They had psychiatric problems. They dreamed of food or breaking their diet. They were anxious and depressed; some were suicidal. They hid food in their rooms. Researchers warn that it is possible that weight reduction doesn’t result in normal weight, but in an abnormal state resembling that of starved non-obese people. Thin people, however, suffer from the opposite: They have to make a great effort to gain weight. Ethan Sims, of the University of Vermont, got prisoners to volunteer to gain weight. In four to six months, they ate as much as they could. They succeeded in increasing their weight by 20 to 25 percent. But months after the study ended, they were back to normal weight and stayed there. This did not mean that people are completely without hope in controlling their weight. It means that those who tend to be fat will have to constantly battle their genetic inheritance if they want to significantly lower their weight. The findings also provide evidence for something scientists thought was true--each person has a comfortable weight range. The range might be as much as 9kg. Someone might weigh 60-69kg without too much effort. But going above or below the natural weight range is difficult. The body resists by feeling hungry or full and changing the metabolism to push the weight back to the range it seeks. What did Ethan Sims make his subjects do
微信支付 
支付宝支付