单选题People and animals that are _________ are hostile and unfriendly. A. inimical B. derelict C. facetious D. aberrant

单选题 The amount of floating plastic trapped in a north Atlantic current system hasn't got any bigger in 22 years, despite more and more plastic being thrown away. Since 1986 students taking samples of plankton (浮游生物) in the Atlantic and Caribbean Oceans have also noted when their nets caught plastic litter. Kara Lavender and colleagues at the Sea Education Association in Woods Hole, Massachusetts, analysed the data, and found that of 6,136 samples recorded, more than 60 per cent included pieces of plastic, typically just millimetres across. The areas of highest plastic concentration are within the north Atlantic sub-tropical gyre (环流), where currents gather the litter. Lavender and her team were surprised to find that the amount of floating plastic had not increased in the gyre. Although it has been illegal since the 1970s for ships to throw plastic overboard, Lavender thinks that the overall rate of plastic rubbish reaching the ocean will have increased, given the fivefold increase in global production of plastic since 1976. 'Where the extra plastic is going is the big mystery,' she says. Plastic resists bio-degradation and can last decades or more in the ocean. Eventually sunlight and wave motion break it into smaller pieces, which can be harmful to marine life—blocking the stomachs of fish and seabirds, for example. Some experts suggest that the plastic might be degrading into pieces small enough to pass through the 0.3-millimetre-mesh nets used in the study, or becoming coated in biofilms and sinking out of range of the nets. However it is unclear why the rate of degradation during the study period should have increased to offset the extra plastic going into the ocean. Lavender says it is unlikely that ocean currents are pushing plastic out of the gyre, although Simon Boxall of the National Oceanography Centre in Southampton, UK, who wasn't involved in the study, disagrees. He says the Atlantic gyre has an exit strategy in the form of the Gulf Stream. 'We've seen high levels of plastic in the Arctic.' he says. Wherever it is going at the moment, the plastic on our oceans will eventually be broken down into microscopic pieces and individual molecules whose environmental effect is unknown. 'The million-dollar question is, is it causing any damage?' says Boxall. 'When plastic particles get so small are they just like fibre going through the system? Some studies suggest that persistent chemicals in newer plastics function as endocrine (内分泌) disruptors and simulated hormones.' And this fine-grained plastic is very long-lived. 'The depressing thing is it's likely to remain in the oceans essentially forever,' says Lavender.

单选题______ student with a little common sense should be able to answer the question.

单选题After the surface is polished, a design is ______ or painted.

单选题We'll all take a vacation in the mountains as soon as I finish working ______ my project.

单选题How much of the world's land surface is at risk of becoming desert?

单选题Since she was alone, she opened the door ______, leaving the chain lock fastened. A.warily B.consciously C.audaciously D.recklessly

单选题It used to take Redwood City, California police hours to locate gunfire. Now, they have a new tool that helps them find the gunfire quickly. This new tool is called the ShotSpotter. The police began using the ShotSpotter in 1995. They wanted to cut down on gunfire in their city. One ShotSpotter covers a square mile. Eight microphones are put on the roofs of buildings. These microphones pick up gunfire noise. It only takes seven seconds to report the gunfire to the police. Then a red dot on the police map shows where the action is. The ShotSpotter really works well. It locates the gunfire within 20 to 40 feet plus or minus. Redwood City police are very happy with the ShotSpotter. They think it might have helped catch the D.C. sniper. ShotSpotters cost a lot of money. One of them sells for $200,000. Despite the cost, ShotSpotters can be a big help in fighting crime.

单选题Many a student ______ something about Abraham Lincoln． A．have known B．knows C．is known D．are known

单选题In 1844, Charles Sturt, a British soldier and colonial administrator, made an expedition ______ a supposed inland sea; his party penetrated more than 1000 miles northward, almost to the center of Australia. A. in quest of B. with regard to C. in favor of D. by way of

单选题Even plants can run a fever, especially when they're under attack by insects or disease. But unlike humans, plants can have their temperature taken from 3,000 feet away — straight up. A decade ago, adapting the infrared scanning technology developed for military purposes and other satellites, physicist Stephen Paley came up with a quick way to take the temperature of crops to determine which ones are under stress. The goal was to let farmers precisely target pesticide (杀虫剂) spraying rather than rain poison on a whole field, which invariably includes plants that don't have pest (害虫) problems. Even better, Paley's Remote Scanning Services Company could detect crop problems before they became visible to the eye. Mounted on a plane flown at 3,000 feet at night, an infrared scanner measured the heat emitted by crops. The data were transformed into a color-coded map showing where plants were running "fevers". Farmers could then spot-spray, using 40 to 70 percent less pesticide than they otherwise would. The bad news is that Paley's company closed down in 1984, after only three years. Farmers resisted the new technology and long-term backers were hard to find. But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to get back into operation. Agriculture experts have no doubt the technology works. "This technique can be used on 75 percent of agricultural land in the United States." says George Oerther of Texas A&M. Ray Jackson, who recently retired from the Department of Agriculture, thinks remote infrared crop scanning could be adopted by the end of the decade. But only if Pale3i finds the financial backing which he failed to obtain 10 years ago.

单选题Very few scientists ______ completely new answers to the world's problems. A. come up with B. come out C. come round D. come up to

单选题The doctor (told) him that he (should take) this medicine (one) pill at (one) time.A. toldB. shouldC. oneD. one

单选题It’s no use ______over spilt milk.

单选题This ambitious project, ______ scores of organizations around the world, will take at least ten years to be accomplished.

单选题He has never seen the Greens and he knows ______ about them.

单选题Jane always enjoys ______ to popular music at home on Friday evenings. A) listening B) being listening C) to be listening D) to listen