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听力原文： I want to talk today about some studies. They seem to indicate that there is a startling world-wide decline in the number of amphibians, such as flogs, toads and salamanders. There's little doubt that one reason why the number of amphibians is declining is their habitats have been destroyed when the developers fill in ponds and marshes to build houses. Amphibians can't just move somewhere. They need water to lay their eggs in. Another problem is the growing fish industry. Another range of popular pool fish such as carp have been introduced to many lakes and ponds all over the world. Raising and selling these fish can be profitable, but the fish eat the eggs and offspring of amphibians that were already living in the lakes and ponds. Other factors could be contributing to the decline include acid rain and the spread of pesticide residues. Many pesticides that farmers added to their crops are eventually washed away bythe rain and end upin pondsand other bodies of water where amphibians live. Amphibians are especially vulnerable to pesticides dissolved in the water because of their moist skins. Water can pass through amphibians allowing toxins dissolved in the water to enter the amphibians'body.
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Why is such a basic health service so easily knocked out？ Mainly because private companies have had little incentive to pursue it. To create a single dose of flu vaccine, a manufacturer has to grow live virus in a 2-week-old fertilized chicken egg, then crack the egg, harvest the virus and extract the proteins used to provoke an immune response. Profit margins are narrow, demand is fickle and, because each year's flu virus is different, any leftover vaccine goes to waste. As a result, the United States now has only two major suppliers (Chiron and Aventis Pasteur)--and when one of them runs into trouble, there isn' t much the other can do about it. "A vaccine maker can't just call up and order 40 million more fertilized eggs," says Manon Cox, of Connecticut-based Protein Sciences Corp. "There's a whole industry that's scheduled to produce a certain number of eggs at a certain time. "
Sleeker technologies are now in the works, and experts are hoping that this year's fiasco will speed the pace of innovation. The main challenge is to shift production from eggs into cell cultures--a medium already used to make most other vaccines. Flu vaccines are harder than most to produce this way, but several biotech companies are now pursuing this strategy, and one culture-based product (Solvay Pharmaceuticals' Invivac) has been cleared for marketing in Europe.
For Americans, the immediate challenge is to make the most of a limited supply. The government estimates that 95 million people still qualify for shots under the voluntary restrictions announced last week. That' s nearly twice the number of doses that clinics will have on hand, but only 60 million Americans seek out shots in a normal year. In fact, many experts are hoping the shortage will serve as an awareness campaign--encouraging the people who really need a flu shot to get one.
Shortages of flue vaccine show that ______.
Part A
Directions: Read the following texts and answer the questions which accompany them by choosing A, B, C or D. Mark your answers on ANSWER SHEET 1.
Not long ago, a mysterious Christmas card dropped through our mail slot. The envelope was addressed to a man named Raoul, who, I was relatively certain, did not live with us. The envelope wasn't sealed, so I opened it. The inside of the card was blank. Ed, my husband, explained that the card was both from and to the newspaper deliveryman. His name was apparently Raoul, and Raoul wanted a holiday tip. We were meant to put a check inside the card and then drop the envelope in the mail. When your services are rendered at 4 a. m. , you can't simply hang around, like a hotel bellboy expecting a tip. You have to be direct.
So I wrote a nice holiday greeting to this man who, in my imagination, fires The New York Times from his hike aimed at our front door, causing more noise with mere newsprint than most people manage with sophisticated black market fireworks.
With a start, I realized that perhaps the reason for the 4 a.m. —wake-up noise was not ordinary rudeness but carefully executed spite: I had not tipped Raoul in Christmases past. I honestly hadn't realized I was supposed to. This was the first time he'd used the card tactic. So I got out my checkbook. Somewhere along the line, holiday tipping went from an optional thank-you for a year of services to a Mafia-style. protection racket (收取保护费的黑社会组织)
Several days later, I was bringing our garbage bins back from the curb when I noticed an envelope taped to one of the lids. The outside of the envelope said MICKEY. It had to be another tip request, this time from our garbage collector. Unlike Raoul, Mickey hadn't enclosed his own Christmas card from me. In a way, I appreciated the directness. "I know you don't care how merry my Christmas is, and that's fine," the gesture said. "I want $ 30, or I'll 'forget' to empty your garbage bin some hot summer day."
I put a check in the envelope and taped it back to the bin. The next morning, Ed noticed that the envelope was gone, though the trash hadn't yet been picked up: "Someone stole Mickey's tip !" Ed was quite certain. He made me call the bank and cancel the check.
But Ed had been wrong. Two weeks later, Mickey left a letter from the bank on our steps. The letter informed Mickey that the check, which he had tried to cash, had been cancelled. The following Tuesday morning, when Ed saw a truck outside , he ran out with his wallet. "Are you Mickey？"
The man looked at him with scorn. "Mickey is the garbageman. I am the recycling. " Not only had Ed insulted this man by hinting that he was a garbageman, but he had obviously neglected to tip him. Ed ran back inside for more funds. Then he noticed that the driver of the truck had been watching the whole transaction. He peeled off another twenty and looked around, waving bills in the air. "Anyone else？"
Had we consulted the website of the Emily Post Institute, this embarrassing breach of etiquette (礼节) could have been avoided. Under "trash/recycling collectors" in the institute' s Holiday Tipping Guidelines, it says, " $10 to $ 30 each. " You may or may not wish to know that your pet groomer, hairdresser, mailman and UPS guy all expect a holiday tip.
The newspaper deliveryman put a blank card inside the envelope because ______.
It was once thought that air pollution affected only the area immediately around large cities with factories and/or heavy automobile traffic. Today, we know that although these are the areas with the worst air pollution, the problem is literally worldwide. On several occasions over the past decade, a heavy cloud of air pollution has covered the entire eastern half of the United States and led to health warnings even in rural areas away from any major concentration of manufacturing and automobile traffic. In fact, the very climate of the entire earth may be affected by air pollution. Some scientists feel that the increasing concentration of carbon dioxide (二氧化碳) in the air revolting from the burning of fossil fuels (coal and oil) is creating a "greenhouse effect"—holding in heat reflected from the earth and raising the world's average temperature.
If this view is correct and the world's temperature is raised only a few degrees, much of the polar ice cap will melt and cities such as New York, Boston, Miami, and New Orleans will be under water.
Another view, less widely held, is that increasing particular matter in the atmosphere is blocking sunlight and lowering the earth's temperature—a result that would be equally disastrous. A drop of just a few degrees could create something close to a new ice age, and would make agriculture difficult or impossible in many of our top farming areas. At present we do not know for sure that either of these conditions will happen (though one recent government report prepared by experts in the field concluded that the greenhouse effect is very likely). Perhaps, if we are very lucky, the two tendencies will offset each other and the world's temperature will stay about the same as it is now.
As is pointed out at the beginning of the passage, people used to think that air pollution ______.
反硝化作用可以在北极冻原和地下深层缺氧的条件下进行。()
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