单选题All (living) things are (made up of) one or more cells, and each of these cells (were) produced by an (already existing) cell.

单选题Few substance on Earth equal the beauty of gemstones such as twinkling diamonds, green emeralds, red rubies, blue sapphires, and multicolored opals.

单选题Hurricanes Hurricanes are migratory tropical cycles that originate over water in certain regions near the equator, particularly over the Caribbean Sea and the Gulf of Mexico. Light breezes alternate here with frequent periods of brisk squalls or stronger winds, as well as intermittent calms. A similar phenomenon occurs in the Western Pacific; these Pacific tropical storms are known as typhoons. Most hurricanes that affect the American continents originate in a narrow belt just north of the Equator called the doldrums. A hurricane consists of high velocity winds blowing circularly around a low-pressure center, which is known as the eye of the hurricane. The low-pressure center develops when warm, saturated air common in the doldrums is under-run and forced upward by denser, cooler air. Hurricanes may be up to I50 miles in diameter, and gale winds may prevail over an area as large as 300 miles in diameter. As one moves from the edge of the storm towards the center, the pressure drops and the intensity of the wind increases. Meteorologists rank hurricanes on a scale of 1 to 5. The least severe category 1 hurricanes have winds of at least 74 miles per hour, while the much stronger and rarer category 5 hurricanes have winds exceeding 155 miles per hour. Within the eye of the storm, the wind"s intensity is far more reduced and the clouds lift, yet the seas remain extremely violent underneath. The hurricane season varies in length according to its region of origin, although generally speaking it peaks worldwide at the end of the summer season in September, and wanes altogether during a brief period in May. That seasonal pattern is due to changes in surface water temperature. Thus, the difference between ocean temperatures and atmospheric temperature is the greatest in the summer, which explains the unusual frequency of hurricanes during the upcoming month of September. However, regional variations in the onset and end of a hurricane season can be observed throughout the globe. In the Atlantic region, hurricanes occur typically from June to November, with a sharp peak in September. The Pacific hurricane season usually lasts all year round, although it records most activity in September and least power in February. In the Indian Ocean, the pattern shifts slightly from April to December, with an upsurge in May and November, whereas in the Southern Hemisphere the trend is from October to May with a spike in February or March. The National Hurricane Center is located in Florida and tracks each storm on a virtual map right from its beginning to its end. A system for tracking hurricanes was developed in the 1950s and improvements have occurred periodically over the years. Scientists are now much more able to accurately make predictions regarding hurricanes, and this has helped minimize loss of life. However, scientists cannot stop hurricanes from developing altogether, and they continue to pose a threat, particularly in coastal regions. 1992"s Hurricane Andrew devastated large areas of Florida and the Caribbean leaving 50 dead, thousands homeless and causing property damage of approximately 12 billion dollars. While most hurricanes are not that severe, Andrew was a reminder that hurricanes have the capacity to wreak havoc and disrupt lives. Glossary equator: a circle that divides a sphere or other surface into congruent parts doldrums: a region of the ocean near the equator, characterized by calms, light winds, or squalls diameter: a straight line segment passing through the center of a figure, especially of a circle or sphere, and terminating at the periphery reminder: a message that helps you remember something

单选题In the early eighteenth century, Ohio grew from a virtual wilderness to become-------of the early states had been in 1776,

单选题(Different fourteen) crops were (being grown) 8,600 years (ago) by some of the world's earliest (farmers).

单选题By 1830 the glass industry in the United States had become too well established that the country no longer needed to depend on imported glass.

单选题Roots of plants tend to grow downward into soil, unless-----more readily available at the surface.

单选题The fluoroscope makes ______ for medical doctors to view a silhouette of the bones and internal organs of a patient's body.

单选题Airline Alliances Cooperative competition. Competitive cooperation. Confused? Airline alliances have travelers scratching their heads over what's going on in the skies. Some folks view alliances as a blessing to travelers, offering seamless travel, reduced fares and enhanced frequent-flyer benefits. Others see a conspiracy of big businesses, causing decreased competition, increased fares and fewer choices. Whatever your opinion is, there are no escaping airline alliances: the marketing hype is {{U}}unrelenting{{/U}}, with each of the two mega-groupings. Oneworld and Star Alliance promote themselves as the best choice for all travelers. And, even if you turn away from their ads, chances are they will figure in any of your travel plans. But why, after years of often ferocious competition, have airlines decided to band together? Let's just say the timing is mutually convenient. North American Airlines, having exhausted all means of earning customer loyalty at home, have been looking for ways to reach out to foreign flyers. Asian carriers are still hurting from the region—the wide economic downturn that began two years ago just when some of the airlines were taking delivery of new aircraft. Alliances also allow carriers to cut costs and increase profits by pooling manpower resources on the ground (rather than each airline maintaining its own ground crew) and code-sharing—the practice of two partners selling tickets and operating only one aircraft. So alliances are terrific for airlines—but are they good for the passenger? Absolutely, say the airlines: think of the lounges, the joint FFP (frequent flyer programme. benefits, the round-the-world fares, and the global service networks. Then there is the promise of "seamless" travel: the ability to, say, travel from Singapore to Rome to New York to Rio de Janeiro, all on one ticket, without having to wait hours for connections or worry about your bags. Sounds Utopian? Peter Buecking, Cathay Pacific's Director of Sales and Marketing, thinks that seamless travel is still evolving. "The key to seamlessness rests in infrastructure and information sharing. We are working on this." Henry Ma, spokesperson for Star Alliance in Hong Kong, lists some of the other benefits for customers: "Global travelers have an easier time making connections and planning their itineraries." Ma claims alliances also assure passengers consistent service standards. Critics of alliances say the much {{U}}touted{{/U}} benefits to the customer are mostly pie in the sky, that alliances are all about reducing costs for the airlines, rationalizing services and running joint marketing programmes. Consumer Report's Senior Editor Jeff Blyskal says the promotional ballyhoo over alliances is much ado about nothing. "I don't see much of a gain for consumers: alliances are just a marketing {{U}}gimmick{{/U}}. Most airlines can not even get their own connections under control, let alone coordinate with another airline. " Blyskal believes alliances will ultimately result in decreased flight choices and increased costs for consumers. Instead of two airlines competing and each operating a flight on the same route at 70% capacity, the allied pair will share the route and run one full flight. Since fewer seats will be available, passengers will be obliged to pay more for tickets. The truth about alliances and their merits probably lies somewhere between the travel Utopia presented by the players, and the evil empires portrayed by their critics. And how much they affect you depends on what kind of traveler you are. Those who've already made the {{U}}elite{{/U}} grade in the FFP of a major airline stand to benefit the most when it joints an alliance: then they enjoy the FFP perks and advantages on any and all of the member carriers. For example, if you are a Marco Polo Club "gold" member of Cathay Pacific's Asia Miles FFP, you will automatically be treated as a valuable customer by all members of Oneworld, of which Cathay Pacific is a member. For those who haven't made the top grade in any FFP, alliances might be a way of simplifying the earning of frequent flyer miles. For example, I belong to United Airline's Mileage Plus and generally fly less than 25000 miles a year. But I earn miles with every flight I take on Star Alliance member—All Nippon Airways and Thai Airways. A. [■] if you fly less than I do, you might be smarter to stay out of the FFP game altogether. B. [■] The only real benefit infrequent flyers can draw from an alliance is an inexpensive round-the-world fare. C. [■] The bottom lines for all the marketing hype, alliances aren't all things to all people—but everybody can get some benefit out of them. D. [■]

单选题According to the passage, what do squirrels do when large quantities of acorns are available?

单选题Listen to Track 2. A. To ask the man to clarify his request B. To state the man's request more precisely C. To make sure that she heard the man correctly D. To correct a mistake the man has made

单选题Ruminants--cattle, bison, sheep, goats, deer, antelopes, and giraffes--have a large four-chambered stomach that enables them to digest fibrous plant matter. When a ruminant first swallows a mouthful of grass or leaves, the food enters the stomach's first chamber, the rumen, where bacteria start to break down the cellulose-rich matter and form it into small balls of cud. The ruminant periodically returns the cud to its mouth where it is chewed at length to crush the fibers, making them more accessible to further bacterial action. The ruminant then reswallows the cud, which passes through the other three chambers of the stomach for further digestion. 5. Which sentence below best expresses the essential information in the highlighted sentence in the passage?

单选题1. What is the speaker's main point? A. Attitudes toward aging can affect how long a person lives. B. People have difficulty learning new skills as they get older. C. Young adults generally have a negative view of older adults. D. People are now living longer than they did in the past. ABCD A [解析] One study on aging suggests that the key to a longer life might be the way you think about yourself as you get older, that is, how you see your own aging. The researchers found that people who view aging positively live longer than people who view it negatively.This study began 26 years ago and took place in a small town in the Midwest. The participants were 640 men and women who were 50 to 90 years old at the time. The sub iects were asked to agree or disagree with statements about aging ... for example, statements like "As you get older, you become less useful" and "Older people can't learn new skills." The data showed that respondents with the most positive attitudes survived a median of 22 years after their initial interview, while those with negative views lived just 15 years--a difference of seven years.What is the speaker's main point?The speaker's main point is that attitudes toward aging can affect how long a person lives. She says: ...the key to a longer life might be the way you think about yourself as you get older...; ...people who view aging positively live longer than people who view it negatively.

单选题The word "demise" in line 12 is closest in meaning to

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单选题Listening1"Professor"sOffice"

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单选题The word "affront" in line 22 is closest in meaning to

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