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Questions 17～20 are based on the following talk. You now have 20 seconds to read Questions 17～20. According to the speaker, how do some pesticides get into ponds
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Questions 11 to 13 are based on a passage on plastic tax. You now have 15 seconds to read Questions 11 to 13. How did plastic industry respond to Lalonde’s petition
World leaders met recently at United Nations headquarters in New York City to discuss the environmental issues raised at the Rio Earth Summit in 1992．The heads of state were supposed to decide what further steps should be taken to halt the decline of Earth’s life-support systems．In fact，this meeting had much the flavour of the original Earth Summit．To wit：empty promises，hollow rhetoric，bickering between rich and poor，and irrelevant initiatives．Think U.S. Congress in slow motion． The writer’s general attitude towards the world leaders meeting at the UN is______． [A] supportive [B] impartial [C] critical [D] comedic
A UCSF study has revealed new information about how the brain directs the body to make movements. The key factor is "noise" in the brain’s signaling, and it helps explain why all movement is not carried out with the same level of precision. Understanding where noise arises in the brain has implications for advancing research in neuromotor control and in developing therapies for disorders where control is impaired, such as Parkinson’s disease. The new study was developed "to understand the brain machinery behind such common movements as typing, walking through a doorway or just pointing at an object," says Stephen Lisberger, PhD, senior study investigator who is director of the W.M. Keck Center for Integrative Neuroscience at the University of California, San Francisco. Study co-investigators are Leslie C. Osborne, PhD, a postdoctoral fellow at UCSF, and William Bialek, PhD, professor of physics at Princeton University. The study findings, reported in the September 15 issue of the journal Nature; are part of ongoing research by Lisberger and colleagues on the neural mechanisms that allow the brain to learn and maintain skills and behavior. These basic functions are carried out through the coordination of different nerve cells within the brain’s neural circuits. "To make a movement, the brain takes the electrical activity of many neurons and combines them to make muscle contractions," Lisberger explains. "But the movements aren’t always perfect. So we asked, what gets in the way" The answer, he says, is "noise", which is defined as the difference between what is actually occurring and what the brain perceives. He offers making a foul shot in basketball as an example. If there were no noise in the neuromotor system, a player would be able to perform the same motion over and over and never miss a shot. "Understanding how noise is reduced to very precise commands helps us understand how those commands are created," says Lisberger, who also is a Howard Hughes Medical Institute investigator and a UCSF professor of physiology. In the study, the research team focused on a movement that all primates are very skilled at: an eye movement known as "smooth pursuit" that allows the eyes to track a moving target. In a series of exercises with monkeys in which the animals would track visual targets, the researchers measured neural activity and smooth pursuit eye movements. From this data, the team analyzed the difference between how accurately the animals actually tracked a moving object and how accurately the brain perceived the trajectory. Findings showed that both the smooth pursuit system and the brain’s perceptual system were nearly equal. "This teaches us that these very different neural processes are limited to the same degree by the same noise sources," says Lisberger. "And it shows that both processes are very good at reducing noise." He concludes, "Because the brain is noisy, our motor systems don’t always do what it tells us to. Making precise movements in the face of this noise is a challenge.\ Of the following movements instructed by the brain, which one is not mentioned in the article
Novel approaches to babymaking seem to be coming at us so fast that we hardly have time to digest one before the next one hits test-tube babies, egg donation, surrogacy, cloning and now sex selection. And just as with earlier methods, the new sperm-separation technique announced last week has triggered plenty of ethical concern. Only a few critics have argued that tampering with nature to avoid a sex-linked genetic disease should be taboo. But plenty have expressed misgivings about using the new technology more casually, to balance families, or simply because parents prefer boys or girls. Such choices, critics say, could lead to an imbalance in the sex ratio, with drastic consequences for society. These arguments are not very persuasive. In some developing countries where boys are more highly valued than girls, sex selection is already standard practice, accomplished by means of infanticide of amniocentesis and abortion. The new sperm-separation technique makes it easier for more people to practice sex selection in these countries. This could skew the already tilting sex radio even further in favor of boys. In the short term, such demographic shifts could cause enormous societal problems as men, for example, find it increasingly difficult to find women to marry. In the long term, however, both evolutionary and economic theories tell us that as girls become more scarce, they will become more highly valued, perhaps to the point at which more people will select for girls than against them. In America and other Western countries there seems to be little chance of the sexes going far out of balance at all. Polls show that a majority of Americans view a perfect family as having one boy and one girl. If everyone used sex selection to achieve perfection, the result would be perfect balance. Of course, some prospective parents do prefer children of one sex or the other. But such preferences would presumably balance out as well. Regarding the argument that choosing gender goes against nature: the same objection was used in earlier times by people horrified by vaccines or heart transplants, which are now completely acceptable. Every time we use medicine to cure a disease or prevent a death, we go against nature willingly. Admittedly, sex selection for family balancing cures no disease. In fact, though, no form of babymaking solves a medical problem. Sex selection, moreover, is medically bengin in comparison with most reproductive technologies. No surgery is involved, and the entire process can theoretically be performed without a physician. Children born through this process can’t be distinguished from other children. For these reasons, I suspect that as sex selection and other reproductive technologies become more efficient and less costly, they may be embraced by American families of even modest means who ask themselves, why not What was once unimaginable could become routine and the link between the sex act and reproduction will no longer be seen as sacred. Ultimately, this may prove to be the real significance of sex selection: by breaching a powerful psychological barrier, it will pave the way for true designer babies, who could really turn society upside down. Which of the following is not a worry to many people about new ways of babymaking
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