With the     1    (develop) of industry, air pollution is getting more and more serious. In Beijing, many people suffer different kinds of illnesses because    2     air pollution.

Air pollution is caused by the     3    (follow) reasons : about half of the problem is caused by vehicles. There are more and more cars, buses on the roads, and they   give off     4    (poison )   gases. 25% of air pollution is caused by factories. Another factor is the smokers. Smoking not only does harm to their health,     5     to others. Besides these, about 10% of air pollution is caused by other reasons.

We should take some    6     (measure) to fight against pollution. New fuel can be used to take     7     place of gas. We can plant     8     (many) trees than before.     9     everybody realizes the importance of environment and does something to stop pollution, the problem will     10    (solve).

The world itself is becoming much smaller by using modern traffic and modern communication means. Life today is much easier than it was hundreds     1    years ago, but it has brought new problems. One of the     2    (big) is pollution. Pollution comes in many     3     (form). We see it, smell it, drink it and even hear it.

Man has been polluting the earth. The more people, the more pollution. Many years ago, the problem was not so serious     4     there were not so many people. When the land was used up or the river was dirty in one place, man     5     (move)to another place. Man is now     6     (slow) polluting the whole world.

Air pollution is still the most serious.Water pollution kills our fish and pollutes our drinking water. Noise pollution     7     (make) us angry more easily.

Many countries are making rules     8     (fight) pollution. They stop people from burning coal in houses and the factories in the city, and from     9     (put) dirty smoke into the air.

The earth is our home. We must take care of     10    . That means keeping the land, water and air clean.

Arctic foxes live on the land and sea ice within the Arctic Circle. Winter in the Arctic is unlike winter in most parts of the world. From October to February, the sun never rises to give    1     (warm)and light.

    2     (luck), these small foxes have     3     (use)adaptation for living in the icy Arctic.Their thick fur coat keeps their body at a comfortable 104°F. Their long tails act like a blanket,     4     (keep)the Arctic foxes warm when they wrap the tails around their body to sleep. And their white coats make it difficult for predators(掠食动物) such as wolves and polar bears to find     5     (they) among the ice and snow.

When they don’t need     6     (avoid) predators or keep warm, Arctic foxes are    7     the hunt for food. They prefer to eat small rodents(啮齿动物), but when times are tough they 'll eat    8     they can find.

If an Arctic fox can't find food, or if the weather    9     (get) really bad, it can dig a snow hole and hunker down(蹲下) for up to two weeks. Once the animal can get out of its hole, it'll try to hunt again. With food in its belly, the Arctic fox has     10     better chance of making it through another long, dark winter.

With the rapid extinction of many wild species, more and more people come to realize the great importance of wildlife protection.

We have to understand the problem in     1     new light: we protect ourselves through protecting wildlife. On the one hand, any species of wildlife helps to keep the ecological balance(生态平衡).     2     one species becomes extinct, it will disappear forever. What is more, it will result     3     the extinction of a chain of wildlife, which may lead to unpredictable disasters. On the other hand, the modern science and technology makes     4    possible for us to learn more about wildlife. By now, scientists     5    (find) that wildlife has unknown genetic codes(遗传密码), which may turn out     6     (free) human beings from serious diseases and     7     (nature) disasters in the future.

It is necessary for us to protect wildlife     8    (immediate) before it is too late, although man has already polluted the environment and threatened the     9    (exist) of many wild species. Let’s take action to protect wildlife.     10    (learn) to live in harmony with all wildlife is part of modern civilization.

The first Smokey Bear poster shows a brown-coated bear wearing jeans. He is staring     1     （shy） up from under a campaign hat as he pours a bucket of water over a campfire. “SMOKEY SAYS,” the poster     2    （read） , “Care will prevent 9 out of 10 forest fires!”

Albert Staehle, the illustrator, chose a bear because he might have wanted Smokey     3     （look） like the father of the forest, as his wife supposed. But many will forever associate the cartoon with a real baby bear,     4     paws（爪子）were burnt in a 1950 spring wildfire.

The baby bear had been rescued by Ray Bell, a forest ranger （护林员）     5    （ fight） a fire in New Mexico's Capitan Mountains. Don Bell was 15 when his father came home with the five-pound bear. The Bell family was constantly taking in wild animals to protect them     6     potential dangers, so Don Bell didn't think much of the "cute little guy" who slept in a rabbit cage. But the story of the rescued baby bear would become     7     national phenomenon. At the capital airport, the     8     （arrive） of Smokey drew hundreds of reporters, photographers and onlookers, and he appeared in     9    （newspaper） across the country.

At the zoo, Smokey drew millions of visitors during 26 years. Having a living animal symbol helped make the wildfire-safety campaign more visible. The Smokey ads were also a far     10    （ good） choice.

Up to June 23rd , 2020, 55 BeiDou satellites     1     (send) up，meaning the completion of China's self-developed BeiDou Navigation(导航) Satellite System (BDS). BDS appears later     2     America's GPS, Russia's GLONASS and EU's Galileo, but it can match them. As one of the fourth     3     (globe) navigation satellite systems, BDS involves efforts of over 400 agencies and 300,000 research personnel and technicians.

Originally     4     (plan) in the 1980s, the network represents a milestone in China's space effort. BDS is comparable to GPS in terms of the     5     (accurate) of positioning. It also offers short message communication and thus can provide emergency communications in areas     6     conventional communication signals are poor.     7     an effort to improve the quality of their positioning services, Apple and Samsung phones, among others, are already using BDS's signals, and so     8     (be) every Chinese brand.

The construction of complete BDS is a huge technical achievement for China and can     9     (easy) pay off in the near future. Meanwhile, BDS's great contribution to     10     (promote) the world's economic and social development as well as the peaceful use of space has attracted the world's attention.

Twelve laureates were awarded a Nobel Prize in 2020. Their achievements are     1     （benefit）to humankind.

Three scientists, Roger Penrose, Reinhard Genzel and Andrea Ghez,     2     helped uncover the details about black holes, shared this year's Nobel Prize in Physics.

Black holes are massive objects whose gravitational field is so strong     3     nothing can escape it, not even light. At their centers, the laws of physics stop making sense.

No question, these objects are mysterious. Fortunately, the full picture gets clearer than before with scientists     4    （ continuous） working on them. Penrose eventually performed mathematical     5    （ calculation） that showed black holes were not just mathematical ideas     6    （ suggest） by

Einstein^’s theory but that they could form in conditions which are likely to exist in the universe. Using the world’s largest telescopes, Genzel and Ghez each lead astronomers who , since the early 1990s,    7    （focus） on a region called Sagittarius A * （人马座 A 星）at the centre of our galaxy. They     8           （ develop） methods to see through the huge clouds of interstellar （星云）gas and dust     9     the centre of the Milky Way. They also improved new techniques,    10    （ devote） themselves to long-term research. Their pioneering work has given us the most convincing evidence of a supermassive black hole at the centre of the Milky Way.