1 . How Climate Change Affects Airline Flights

Hot weather has forced dozens of commercial flights to be canceled at airports in the Southwest this summer. This flight-disturbing _______ is a warning sign. Climate change is projected to have far-reaching _______—including sea level rise flooding cities and shifting weather patterns causing long-term declines in agricultural production. And there is evidence that it is beginning to affect the takeoff performance of commercial aircraft, with potential effects on airline _______.

National and global transportation systems and the economic activity they support have been designed for the climate in which it all developed. In the aviation (航空) industry, airports and aircraft are designed for the weather conditions experienced _______. Because the climate is changing, even fundamental elements like airports and key economic parts like air transportation may need to be_______.

As scientists focused on the impacts of climate change and extreme weather on human society and natural ecosystems around the world, our research has quantified how extreme heat associated with our warming climate may affect _______ around the world. We’ve found that major airports from New York to Dubai to Bangkok will see more frequent takeoff weight _______ in the coming decades due to increasingly common hot temperatures, which can help reduce the aircraft’s weight so as to lower its required takeoff speed.

There is obvious evidence that extreme events such as heat waves and coastal flooding are happening with greater frequency and intensity than just a few decades ago. And if we _______ to reduce greenhouse gas emissions significantly in the next few decades, the frequency and intensity of these extremes is projected to increase dramatically.

The _______ on aviation may be widespread. Many airports are built near sea level, putting them at risk of more frequent ________ as oceans rise. The frequency and intensity of violent air movement may increase in some regions due to strengthening high-altitude (高海拔的) winds. Stronger winds would force airlines and pilots to change flight lengths and routings, potentially increasing fuel ________.

Many departments of the economy, including the aviation industry, have yet to seriously ________the effects of climate change. The sooner, the better: Both airport construction and aircraft design take decades, and have ________ effects. Today’s newest planes may well be flying in 40 or 50 years, and their ________ are being designed now. The earlier climate impacts are understood and appreciated, the more effective and less costly adaptations can be. Those adaptations may even include innovative ways to dramatically reduce climate-altering emissions across the aviation industry, which would help reduce the problem while also ________ it.

2 . One of the most pressing challenges the world will face in the next few decades is how to relieve the growing stress that human activities are placing on the environment. The consequences are just too great to_______. Wildlife habitats are disappearing as new developments._______more land. Plant and animal species are getting in_______at a greater rate now than at any time in Earth’s history. As many as 30 percent of the world’s fish stocks are over-exploited. And the list goes on.

_______, there is reason to have hope for the future. Advances in computing power and molecular biology are_______the tremendous increases in scientific capability that are helping researchers_______a better understanding of these problems. Recent development in science and technology could provide the_______for some major and timely actions that would improve our understanding of how human activities affect the environment.

One priority (优先处理的事) for research is improving hydrological (水文学的) forecasting. It is_______that the world’s water use will triple (变成三倍) in the next two decades. Already, widespread water_______has occurred in parts of China, India, and North Africa. The need for water also is taking its toll (造成痛苦) on fresh water ecosystems in the United States. Only 2 percent of the nation’s streams are considered in good__________, and close to 40 percent of native fish species are threatened with__________.

To__________outbreaks of infectious diseases in plants, animals and human, more study is needed on how parasites (寄生虫) and disease-carrying species — as well as humans and other species they__________— are affected by changes in the environment. The overuse of antibiotics both in humans and in farm animals has__________the growth of antibiotic- resistant microorganism (微生物). Researchers can__________new technologies in genetics and computing to better monitor and predict the effects that environment changes might have on disease outbreaks.

4 . Imagine that you're an insect，and that you have fallen ill because some bacteria or parasites have attacked your body. If you want to make it to a ripe old_______age，your body will need to fight off these_______.

The problem is that if you're an insect，your_______span may be only a few days long. This means that _______humans，you simply don't have the time to relax yourself in bed，watching TV and waiting for your body to_______how to fight off each disease it comes across.

Still，there's no reason for your insect self to be_______and thus lose calmness. Evolution has_______you with what scientists call inborn immunity，which you take over from your parents. Inborn immunity means that your bug body has the power to_______recognize and destroy many_______enemies.

In your bug body there is a fluid called hemolymph（血淋巴），which is________to human blood. If you're________，elements in the hemolymph interact with specialized cells in your immune system to thicken and form a hard dry covering over the________of the wound that locks your wound and prevents infection. The hemolymph also contains proteins that are ready to________enemies like bacteria or fungi. However，some attackers，like tiny parasitic insects，may be too large for the proteins to________.

In this case，your body encloses the enemy and walls it off from the rest of the body. The enveloped enemy then stays inside you for the rest of your________insect life，or until you fly into a windshield，whichever comes first.

5 . The American elm tree, with its soaring height and gracefully arching branches, was once a common sight throughout the eastern half of the United States. Yet by 1969, ninety percent of the American elms were______or dying.

How did this happen? By the early 1900s, the European______of the American elm had caught a fungal disease. The fungus that causes the disease was first identified in the Netherlands, which is why the disease is referred to as Dutch elm disease even though it is believed to have originated______. The fungus is spread by the elm bark beetle. Some elm logs,______to the United States from France in 1932, were _____both the deadly fungus and the beetles. Within a short time, the beetles had______the fungus to American elm trees.

To fight this disease, scientists crossbred American elms with European and Asiatic elms to create a disease-resistant hybrid. But these hybrids lack the characteristic______and beauty of the American elm. Another disease-resistant elm-the Liberty elm-was______by genetic breeding. However, the cell structure of the Liberty elm is different from that of the American elm. Tree growers were still not______.

In the late 1970s, scientists tried another plan. Here and there around the countryside a few American elm trees had______the disease. Scientists reasoned that these trees must have a(n)______resistance to the Dutch elm disease. They grew cuttings from these trees and______them to the fungus. Some of the trees developed the disease, but two varieties-the Valley Forge elm and the New Harmony elm -developed no symptoms. Although neither variety is______resistant to the disease, both show a high level of______to the fungus. After more than twenty years of research, scientists are confident that they have found a solution, if not a______, for the problem. The Valley Forge elm and the New Harmony elm will soon replace the lost icons of the American landscape.

6 . Growing Adoption of Green Cleaning

When we clean the bathroom, we’ve got all kinds of stuff to help us out: a cleaning solution that removes dirty marks from the shower walls and something in a squeeze bottle that makes the toilet sparkling clean. When all is done, the room is neat and clean,_____________dirt and bacteria. There’s just one problem—the_________ we used to clean can be harmful to people   and the environment. For this reason, many people say that traditional cleaners should be_______and replaced with less harmful “green” products.

The problem_________the fact that some cleaning products contain harsh chemicals that just aren’t healthy for humans, animals, or the planet. Think of the_______coming from a factory and getting into the air. The smoke creates air pollution, which harms the environment and makes us feel ill when we breathe it in.___________, the chemicals in cleaning products pollute the air and can hurt us when we breathe them in or when they get on our skin. However, not all cleaning products are harmful. Green products, which do not contain harsh chemicals, are said to be good_______ because they are effective at cleaning and are safe for people and for the planet.

___________about chemicals has led many states to require schools and government buildings to use environmentally friendly cleaning products instead of products containing   poisonous chemicals. Last year, 10 states required the use of green products and at least 5 other states were considering_________in support of these products. A proposed bill would apply to bathroom and floor cleaners, hand soap, toilet paper, paper towels, and etc.

Many green cleaning products are widely available at prices__________traditional products. In some cases, manufacturers receive green certifications for products they have long had on the market, and the prices of these products remain low. But not everyone shares the view about the

____________of green products. Toilet paper, trash bags and paper towel made from recycled materials can cost up to 20% more than traditional products, said Stephen, director of the Green Cleaning Network.

So,____________of the proposed legislation are concerned about the potentially higher costs for some green products. These critics say that states should not determine which products________ institutes and agencies must buy, especially if they increase costs, since many universities are already struggling financially. Some states have made compromises ( 妥 协 ) to help________ concerns about costs. In Wisconsin, a recent adjustment to the bill would give schools and agencies three years instead of one to begin using green products. It would also________them to quit if they could show that their costs would increase.

7 . China and India Dominate the Greening of Earth

Over the last two decades, the Earth has seen an increase in foliage (植物) around the planet, measured in average leaf area per year on plants and trees. Data from NASA satellites shows that China and India -- two _______ economies with the world's biggest populations -- are _______ the increase in greening on land. The effect comes mostly from _______ tree-planting programs in China and intensive agriculture in both countries.

Researchers from Boston University found that global green leaf area has increased by five percent since the early 2000s, an area _______ to the entire Amazon rainforest. The study was also published in the journal Nature Sustainability on February 11. It revealed that at least 25 percent of the global foliage _______ this century came in China.

"China and India _______ one-third of the greening, but contain only nine percent of the planet's land area covered in vegetation," said lead author Chi Chen of Boston University. "That is a surprising finding, considering the general idea of land degradation(退化) in populous countries from _______."

China's _______ contribution to the global greening trend came in large part from programs to conserve and expand forests, accounting for about 42 percent of the greening contribution. These programs were developed in an effort to _______ the effects of air pollution, soil erosion and climate change.

Another 32 percent of the greening change in China, and 82 percent in India, resulted from intensive ________ of food crops. The land area used to grow crops in China and India has not changed much since the early 2000s. Yet both countries have greatly increased annual total green leaf area and food production in order to ________ large populations.

Rama Nemani, a research scientist at NASA's Ames Research Center, saw a(n) ________ message in the new findings. "Once people realize there is a problem, they tend to fix it," he said. "In the 1970s and 80s in India and China, the situation around vegetation loss was not good. In the 1990s, people realized it, and today things have improved. Humans are ________ resilient (复原快的，适应力强的). That's what we see in the satellite data."

________, the researchers rang bells as well. They pointed out that the gain in global greenness did not ________ make up for the loss of natural vegetation in tropical regions like Brazil and Indonesia.