单选题 Continue to Protect or Destroy Ecosystem Biosphere Ⅱ was a spectacular failure. The gleaming glass-and-concrete habitat sprawling across the desert in Oracle, Arizona, was supposed to support eight human "biospherians" for two years. But the seal has to he broken before the experiment ended in 1993. Oxygen had fallen to levels normally seen at an elevation of 17,500 feet. Nitrous oxide had risen to the point where it threatened to cause brain damage. The fresh water supply became contaminated, and vines smothered (厚厚地覆盖) food plants. Insect pollinators (传授花粉的生物) and many other species became extinct. By the end, Biosphere Ⅱ was overrun with swarms of ants and cockroaches. Scientists who gathered recently to review the Biosphere Ⅱ experiment reached a disturbing conclusion: "No one yet knows how to engineer systems that provide humans with the life-supporting services that natural ecosystems produce for free." The problem is that these ecosystems are undergoing wrenching changes. Water and air quality, while improving in some regions, are deteriorating in many others. Carbon dioxide levels in the atmosphere arc climbing. The world's population could reach 10 billion by 2050. And famed Harvard biologist Edward O. Wilson says the current rate of species losses puts us "in the midst of one of the great extinction spasms (突然进发) of geological history." All of which makes many ecologists wonder whether humans too will soon become extinct. It's an incredibly important but incredibly difficult question. If we continue on this course, we're heading for a world in which we will have to engineer services we've always received for free from nature. That's why the failure of Biosphere Ⅱ was so disturbing: it proves that we don't yet know how to do that. The Biosphere Ⅱ experience demonstrated that maintaining human life is a tricky proposition-especially if we can no longer rely on the services provided by natural ecosystems. If we are currently living through a mass extinction, as Wilson believes, we should consider the past. In the great Permian extinction 245 million years ago, 96 percent of species perished. Eventually, the Earth was repopulated with a rich collection of new species, but it took 100 million years. "That should give pause to anyone who believes that what Homo sapiens (现代人) destroys, nature will redeem," Wilson says. "Maybe so, but not within any length of time that has meaning for contemporary humanity."

单选题The two banks have announced plans to {{U}}merge{{/U}} nest year. A. combine B. sell C. close D. break

单选题The Intemet as the public has known it and used it for the last decade may not be the Interact for the future. The system is getting old and rickety( 快要散架的; 摇摇晃晃的) ,particularly for the volume of commerce it has to accommodate. The prophylactic(预防性的) software that was meant to protect the web is less effective. Like anything else that is used regularly whether it is a ear, a light bulb, or a PC, the Internet is going to have to be patched and upgraded more often now. It won't work every hour of every day anymore. The paragraph is intended to tell the reader thatA. the Internet is working properly till now.B. the Internet used now has many problems.C. the Intemet has to deal with a lot of data.D. the Internet is well protected by softwar

单选题Gardner thinks that his theory has a ________ .

单选题We do not recognize the Uall-comprehensive/U effects of a center on every aspect of our life.

单选题At the policeman's signal, the vehicle pulled up.A. stoppedB. slowed downC. sped upD. turned up

单选题New Product Will Save Lives Drinking water that looks clean may still contain bugs(虫子) , which can cause illness. A small company called Genera Technologies has produced a testing method in three stages, which shows whether water is safe. The new test shows if water needs chemicals added to it, to destroy anything harmful. It was invented by scientist Dr. Adrian Parton, who started Genera five years ago. He and his employees have developed the test together with a British water company. Andy Headland, Genera's marketing director, recently presented the test at a conference in the USA and forecast good American sales for it. Genera has already sold 11 of its tests at $ 42, 500 a time in the UK and has a further four on order. It expects to sell another 25 tests before the end of March. The company says it is the only test in the UK to be approved by the government. Genera was formed five years ago and until October last year had only five employees; it now employs 14. Mr. Headland believes that the company should make around $19 million by the end of the year in the UK alone.

单选题Where Did All the Ships Go? The Bermuda Triangle(三角区)is one 1 the greatest mysteries of the sea. In this triangular area between Florida, Puerto Rico and Bermuda in Atlantic, ships and airplanes 2 to disappear more often than in 3 parts of the ocean. And they do so 4 leaving any sign of an accident or any dead bodies. It is 5 that Christopher Columbus was the first person to record strange happenings in the area. His compass stopped working, a flame came down from the sky, and a wave 100 to 200-feet-high carried his ship about a mile away. The most famous disappearance in the Bermuda Triangle was the US Naval(海军的) Air Flight 19. 6 December 5, 1945, five bomber planes carrying 14 men 7 on a training mission from the Florida coast. Later that day, all communications with Flight 19 were lost. They just disappeared without a trace. The next morning, 242 planes and 19 ships took part in the largest air-sea search in history. But they found nothing. Some people blame the disappearances 8 supernatural(超自然的)forces. It is suggested the 9 ships and planes were either transposed to other times and places, kidnapped(绑架)by aliens(外星人) 10 attacked by sea creatures. There are 11 natural explanations, though. The US Navy says that the Bermuda Triangle is one of two places on earth 12 a magnetic compass(指南针)points towards true north 13 magnetic north. 14 , planes and ships can lose their way if they don"t make adjustments. The area also has changing weather and is known 15 its high waves. Storms can turn up suddenly and destroy a plane or ship. Fast currents could then sweep away any trace of an accident.

单选题There weren't any surprises there. The surprise I had was standing on the surface after we'd been there for a few minutes, having a chance to rest a little bit, and looking up at the earth for the first time-you have to look up because that's where it is. And the sky is totally black, and here you have a planet which is four times the size of the moon as we look at it from the earth, and you also have color. You have a blue ocean and the brown landmasses-the brown continents-and you can see ice on the ice caps on the North Pole, and so on. The speaker was mostly probably talking his experienceA. on the high mountain.B. under the ocean water.C. in an airplane.D. on the surface of the moon,

单选题The man is a mystery for his neighbors.

单选题The cougar behaved strangely because it had sensed the threat of a quake.

单选题We shall keep the money in a secure place.

单选题Jane said that she couldn't tolerate the long hours.A. spendB. standC. takeD. last

单选题This was disaster on Ucosmic/U scale.

单选题Alice laid her baby on the sofa tenderly and wrapped it with a blanket.

单选题 Electronic Teaching The potential of closed-circuit television and other new electronic teaching tools is so great that it is fascinating to visualize "the school of tomorrow". Televised lessons will originate from a central building having perhaps four or five master studios. The lessons will be carried into classrooms all over a city, or even an entire country. After a televised lesson has been given, the classroom teacher will take over for the all-important "follow-up" period. The students will ask any troublesome questions, and difficult points will be cleared up through discussion. The teacher in the classroom will have additional electronic tools. On the teacher's desk, the traditional chalk and erasers will have been replaced by a multiple-control panel and magnetic tape player. The tape machines will run pre-recorded lessons which pupils will follow by headphones. The lessons will be specifically geared to the students' levels of ability. For instance, while the class as a whole studies history, each student will receive an individual history lesson, directed to his particular level of ability. Should question arise, the students will be able to talk directly to the teacher on individual "intercoms" without disturbing the rest of the class. In this way, the teacher will be able to conduct as many as three classes at the same time. With the rapid development of computer science, students will be aided with specially prepared multimedia software to study their subjects better. Homework will possibly be assigned and handed in via electronic mail system. Students can even take examinations on their computer linked with the teacher's and get the score instantly. They will get certificates or diplomas if they pass all the required examinations. Experts believe that this type of education will be very popular in the years ahead.

单选题Without signals from navigation satellites, the in-car computer

单选题The current edition of that magazine discusses the ancient civilization of Latin America.A. firstB. latestC. oldD. special

单选题The new regulations will ______ into force on October 1 next year.A. comeB. becomeC. bringD. begin

单选题The dentist has decided to extract her bad tooth.