Yosemite is a national park in California. It is very beautiful and big. The park includes more than 760,000 acres (英亩) in the California Mountains. Most of the park is wild (荒凉的).

    The part of Yosemite that everyone likes is Yosemite Valley. It is a small valley that is 7 miles long and less than 1 mile wide. It has tall rock walls and streams that flow down in waterfalls. More than two million visitors come to the valley each year.

    It's said that the number of visitors is more than the land can hold. The valley has 4,500 camping places. It has a hotel that can hold 4,000 families. This is still not enough to serve all of the visitors. The valley has grown so big that it has a lot of traffic.

    A worker says the park is trying to keep the beauty of the park and let everyone visit. Some areas have been rounded up (圈起来) to keep people away and planted with seeds to try to keep them beautiful.

    A former worker thinks Yosemite should get more money to take better care of the park. He would also like to teach people what the park service is trying to do.

    Some people are trying to save Yosemite Valley. A plan has been made to remove some buildings. There will be fewer cars allowed inside the park. More buses will help get people around.

    For many people who live in cities, parks are an important landscape. They provide a place for people to relax and play sports, as well as a shelter from the often severe environment of a city. What people often overlook is that parks also provide considerable environmental benefits.

    One benefit of parks is that plants absorb carbon dioxide and give off oxygen. According to one study, an acre of trees can absorb the same amount of carbon dioxide that a typical car emits in 11,000 miles of driving. Parks also make cities cooler. Scientists have long noted what is called the Urban Heat Island Effect: building materials such as metal and concrete (混凝土) absorb much more of the sun's heat and release it much more quickly than trees and grass. Because city landscapes contain so much of these building materials, cities are usually warmer than surrounding rural areas. Parks and other green spaces help to lessen the Urban Heat Island Effect.

    Unfortunately, many cities cannot easily create more parks. However, cities could benefit from many of the positive effects of parks by encouraging citizens to create another type of green space: rooftop gardens. While most people would not think of starting a garden on their roof, human beings have been planting gardens on rooftops for thousands of years. Some rooftop gardens are simple container gardens that anyone can create with the investment (投资) of a few hundred dollars and a few hours of work.

    Rooftop gardens provide many of the same benefits as other urban parks and garden spaces, but without taking up the much-needed land. In the summer, rooftop gardens prevent buildings from absorbing heat from the sun, which can significantly reduce cooling bills. In the winter, gardens help control the heat that materials like brick and concrete release so quickly, leading to savings on heating bills. Rooftop vegetables and herb gardens can also provide fresh food for city settlers, making their diets healthier. Rooftop gardens are not only something everyone can enjoy but also a smart environmental investment.

    The Healthy Habits Survey(调查)shows that only about one third of American seniors have correct habits. Here are some findings and expert advice.

    ⒈How many times did you brush your teeth yesterday?

    Finding: A full 33% of seniors brush their teeth only once a day.

    Step: Remove the 300 types of bacteria in your mouth each morning with a battery­operated toothbrush. Brush gently for 2 minutes, at least twice a day.

    ⒉How many times did you wash your hands or bathe yesterday?

    Finding: Seniors, on average, bathe fewer than 3 days a week. And nearly 30% wash their hands only 4 times a day—half of the number doctors recommend.

    Step: We touch our faces around 3,000 times a day—often inviting germs(病菌)to enter our mouth, nose, and eyes. Use toilet paper to avoid touching the door handle. And, most important, wash your hands often with hot running water and soap for 20 seconds.

    ⒊How often do you think about fighting germs?

    Finding: Seniors are not fighting germs as well as they should.

    Step: Be aware of germs. Do you know it is not your toilet but your kitchen sponge (海绵) that can carry more germs than anything else? To kill these germs, keep your sponge in the microwave for 10 seconds.

    Unlike modern animal scientists, dinosaur scientists cannot sit on a hillside and use telescopes to watch dinosaurs in order to know how they lived and whether they were good parents. Instead, they have to search hard for information from dinosaurs' fossils(恐龙化石) because dinosaurs died out millions of years ago.

    It's very difficult for the scientists to reach an agreement because different results can be got from the same fossils. Many fossils of the same kind of dinosaurs have been dug out from one place. They might have formed when an entire group of dinosaurs got stuck(陷入)all at once. Or they might have been the result of dinosaurs getting stuck one after another over a course of a few centuries. Thus we can say that dinosaurs might have in the first case lived in big groups and in the second lived alone.

    Though there are two different results, dinosaur scientists now generally agree that at least some kinds of dinosaurs lived in big groups. “That's pretty much settled at this point.” Says Paul Sereno. A kind of dinosaurs called Sauropods left behind tracks in the western United States that appear to run north and south, suggesting that they even moved long distances together.

    As to whether dinosaurs cared for their young, dinosaur scientists have turned to the closest living relatives of dinosaurs, birds and crocodiles for possible models. Birds give a lot of care to their young, while crocodiles just help their young to the water. The discovered fossils of dinosaurs sitting on their eggs and staying with their young suggest the parents were taking care of their babies, but we still cannot say that all dinosaurs did the same.

    There is still a long way to go before the above questions could be answered. Dinosaur scientists will have to find more proof to reach an agreement.

    There has, in recent years, been an outpouring of information about the impact of buildings on the natural environment. Information which explains and promotes green and sustainable construction design, strives to convince others of its efficacy (功效) and warns of the dangers of ignoring the issue. Seldom do these documents offer any advice to practitioners, such as those designing mechanical and electrical systems for a building, on how to use this knowledge on a practical level.

    Although there are a good many advocates of "green" construction in the architectural industry, able to list enough reasons why buildings should be designed in a sustainable way, not to mention plenty of architectural firms with experience in green design, this is not enough to make green construction come into being. The driving force behind whether a building is constructed with minimal environmental impact lies with the owner of the building; that is, the person financing the project. If the owner considers green design unimportant, or of secondary importance, then more than likely, it will not be factored into the design.

    The commissioning (委任) process plays a key role in ensuring the owner gets the building he wants, in terms of design, costs and risk. At the predesign stage, the owner's objectives and expectations are discussed and documented. This gives a design team a solid foundation on which they can build their ideas. Owners who skip the commissioning process, or fail to take "green" issues into account when doing so, often come a cropper once their building is up and running. Materials and equipment are installed as planned, and, at first glance, appear to fulfil their purpose adequately. However, in time, the owner realizes that operational and maintenance costs are higher than necessary, and that the occupants are dissatisfied with the results. These factors in turn lead to higher ownership costs as well as increased environmental impact.

    In some cases, an owner may be aware of the latest trends in sustainable building design. However, firms should not take it as read that the client already has an idea of how green he intends the structure to be. Indeed, this initial interaction between owner and firm is the ideal time for a designer to outline and promote the ways that green design can meet the client's objectives, thus turning a project originally not destined for green design into a potential candidate.

    Typically, when considering whether or not to adopt a green approach, an owner will ask about additional costs or return for investment. In a typical project, landscape architects, mechanical and electrical engineers do not become involved until a much later stage. However, in green design, they must be involved from the outset, since green design demands interaction between these disciplines. This increased cooperation clearly requires additional cost. However, there may be financial advantage for the client in choosing a greener design. There are examples of green designs which have demonstrated lower costs for long-term operation, ownership and even construction.

Where does the meat on our table come from? It usually comes from livestock like chickens and cows. But did you know that meat can also be made in a lab? US company JUST has announced that lab-grown meat could be on some restaurant menus in the United States and Asia by the end of 2018, The Independent reported. 

"These meats include chicken nuggets (鸡块), sausage and foie gras (鹅肝酱), " Josh Tetrick, CEO of JUST, told The Independent. Lab meat is sometimes referred to as "clean meat". It is made using the stem cells (干细胞) of living livestock. The cells need to be grown in a lab for a few weeks. For example, making a hamburger patty (肉饼) takes about nine weeks, CNN reported. This is faster than raising a cow, which usually takes over 20 weeks. 

The first clean meat was a beef burger that was produced in 2013, but it was said to taste quite dry. How does clean meat taste now? Clean meat supporters told CNN that they think it tastes just like traditional meat. 

Clean meat has other advantages. It is healthier than traditional meat. Meat producers can control what type of fat goes into the meat. They can produce clean meat that contains healthy fats, such as omega-3 fatty acids (脂肪酸). This kind of fat is good for people's hearts. 

Clean meat can also help to solve global warming. According to The Washington Post, about 14. 5 percent of the planet's greenhouse gas emissions (排放) come from raising livestock. That's more than the emissions from every car, train, ship and airplane in the world combined. It is predicted that switching to clean meat could lower greenhouse gas emissions by 96 percent, The Independent reported.