单选题He is {{U}}certain{{/U}} that the dictionary is just what I want.

单选题Graphene"s Superstrength Big technology comes in tiny packages. New cell phones and personal computers get smaller every year, which means these electronics require even smaller components on the inside. Engineers are looking for creative ways to build these components, and they"ve turned their eyes to graphene, a superthin material, made of carbon, that could change the future of electronics. This year"s Nobel Prize for Physics has been awarded to Andre Geim and Kostya Novoselov from the University of Manchester, UK. for the discovery of graphene. Graphene isn"t just small, it"s "the thinnest possible material in this world," says Novoselov. He calls it a "wonder material." It"s so thin that you would need to stack about 25,000 sheets just to make a pile as thick as a piece of ordinary white paper. If you were to hold a sheet of graphene in your fingers, you"d have no idea because you wouldn"t be able to see it. Carbon is one of the most abundant elements in the universe. Every known kind of life contains carbon. Graphene is a sheet of carbon, but only one atom thick. You don"t have to look far to find graphene—it"s all around you. If you want this high-tech wonderstuff, all you need is a pencil, paper and a little adhesive tape. Use the pencil to shade a small area on the paper, and then apply a small piece of adhesive tape over the area. When you pull up the tape, you"ll see that it pulls up a thin layer of some of the shading from your pencil. That layer is called graphite, one of the softest minerals in the world. Now stick the same piece of tape on another sheet of paper and pull the tape up—there should be an even thinner layer, this time left on the paper. Now imagine that you do this over and over, until you get the thinnest possible layer of material on the paper. This layer would be only one atom thick, and you wouldn"t be able to see it. Graphite is made of layers of graphene, so when you get to the thinnest possible layer, you"ve found graphene.

单选题She stood there, trembling with fear.

单选题Since the Uadvent/U of the motor car, road accidents have increased dramatically.

单选题You need feedback to monitor progress.

单选题Since ancient times people have found various ways to preserve meat.

单选题Her faith upheld her in times of sadness.

单选题It was advisable for you not to mention that.

单选题The Northern Lights The sun is stormy and has its own kind of weather. It is so hot and active that even the Sun"s gravity cannot hold its atmosphere in check! Energy flows away from the Sun toward the Earth in a stream of electrified particles that move at speeds around a million miles per hour. These particles are called plasma (等离子体), and the stream of plasma coming from the Sun is called the solar wind. The more active the Sun, the stronger the solar wind. The solar wind constantly streams toward the Earth, but don"t worry because a protective magnetic field surrounds our planet. The same magnetic field that makes your compass point north also steers the particles from the Sun to the north and south poles. The charged particles become trapped in magnetic belts around the Earth. When a large blast of solar wind crashes into the Earth"s magnetic field, the magnetic field first gets squeezed and then the magnetic field lines break and reconnect. The breaking and reconnecting of the magnetic field lines can cause atomic particles called electrons trapped in the belts to fall into the Earth"s atmosphere at the poles. As the electrons fall to the Earth, they collide with gas molecules in the atmosphere, creating flashes of light in the sky. Each atmospheric gas glows a different color. Oxygen and nitrogen glows red and green and nitrogen glows violet purple. As these various colors glow and dance in the night sky, they create the Northern Lights and the Southern Lights. Watching auroras (北极光) is fun and exciting, but normally you can only see them in places far north like Alaska and Canada. The movement of the aurora across the sky is usually slow enough to easily follow with your eyes but they can also pulsate (跳动), flicker (闪烁), or even move like waves. During solar maximum, 5 auroras are seen as far south as Florida, even Mexico! Auroras often seem to be very close to the ground, but the lowest aurora is still about 100 kilometers above the ground, a distance much higher than clouds are formed or airplanes can fly. A typical aurora band can be thousands of kilometers long, a few hundred kilometers high, but only a few hundred meters thick. We hope you are able to travel to far north places like the Arctic Circle and see the Northern Lights at least once during your lifetime. We know you will never forget it!

单选题He was persuaded to give up the idea.

单选题Sitting in the Land Rover with lions all around, the men felt very Uvulnerable/U.

单选题The manager allocates duties to the clerks. A. assigns B. persuades C. asks D. orders

单选题Shelly had prepared carefully for her biology examination so that she could be sure of passing it on her first endeavor.A. intentionB. attemptC. purposeD. desire

单选题Over thirty cities around the world boast more than five million {{U}}residents.{{/U}}

单选题I was going to speak to an old friend across the room, but she ignored me. A. regretted B. without regard to C. took no notice of D. neglected

单选题His answers were obscure and confusing. A. unclear B. obvious C clear D. direct

单选题 Being thin or not No woman can be too rich or too thin. This saying often attributed to the late Duchess of Windsor embodies much of the odd spirit of our times. Being thin is deemed as such a virtue. The problem with such a view is that some people actually attempt to live by it. I myself have fantasies of slipping into narrow designer clothes. Consequently, I have been on a diet for the better-or worse-part of my life. Being rich wouldn't be bad either, but that won't happen unless an unknown relative dies suddenly in some distant land, leaving me millions of dollars. Where did we go off the track? When did eating butter become a sin and a tittle bit of extra flesh unappealing, if not repellent? All religions have certain days when people refrain from eating, and excessive eating is one of Christianity's seven deadly sins. However, until quite recently, most people had a problem getting enough to eat. In some religious groups, wealth was a symbol of probable salvation and high morals, and fatness a sign of wealth and well-being. Today the opposite is true. We have shifted to thinness as our new mark of virtue. The result is that being fat-or even only somewhat overweight—is bad because it implies a lack of moral strength. Our obsession with thinness is also fueled by health concerns. It is true that in this country we have more overweight people than ever before, and that, in many cases, being overweight correlates with an increased risk of heart and blood vessel disease. These diseases, however, may have as much to do with our way of life and our high-fat diets as with excess weight. And the associated risk of cancer in the digestive system may be more of a dietary problem—too much fat and a lack of fiber—than a weight problem. The real concern, then, is not that we weigh too much, but that we neither exercise enough nor eat well. Exercise is necessary for strong bones and both heart and lung health. A balanced diet without a lot of fat can also help the body avoid many diseases. We should surely stop paying so much attention to weight. Simply being thin is not enough. It is actually hazardous if those who get (or already are) thin think they are automatically healthy and thus free from paying attention to their overall life-style. Thinness can be pure vain glory.

单选题The Value of Advertisement Money spent on advertising is worth spending. It serves directly to bring about a rapid sale of goods at reasonable prices, so setting up a firm home market and making it possible to provide for export at good price. By drawing attention to new ideas it helps greatly to raise standards of living. By helping to increase demand it causes an increased need for labor, and is therefore a nice way to fight unemployment. It lowers the costs of many services: without advertisements your daily newspaper would cost four times as much, the price of your television program would need to be doubled, and travel by bus or subway would cost more. And perhaps most important of all, advertising provides a promise of reasonable value in the products and services you buy. Besides the fact that twenty-seven Acts of Parliament govern the terms of advertising, no regular advertiser dare produce anything that fails to live up to the promise of his advertisements. He might fool some people for a little while through misleading advertising. He will not do so for long, for the public has the good sense not to buy the poor goods more than once. If you see a product frequently advertised, it is the proof I know that the product does what is promised for it, and that it has good value. Advertising does more for the good of the public than any other force I can think of. There is one more point I feel I ought to touch on. Recently I heard a well-known television person declare that he was against advertising because it persuades rather than informs. He was telling us the real difference. Of course advertising tries to persuade. If its messages were nothing but information, that would be difficult to get more people to buy, for even the choice of the color of a shirt is a bit persuasive--advertising would be so boring that no one would pay any attention. But perhaps that is what the well-known television person wants.

单选题The eternal motion of the stars fascinated him. A. long B. never-ending C. boring D. extensive

单选题Do we have to wear these name {{U}}tags{{/U}}? A. lists B. labels C. forms D. codes