根据短文理解，选择正确答案。

    Every minute，someone is setting up an Internet company somewhere, in the world． Each one is searching for the one great idea that could make his web company click in a big way．And they are trying all kinds of tricks to attract people towards their websites．While some websites offer sounds，cartoons and amazing photos on screen to make their sites almost a movie-like experience for the viewers，others provide free downloads and competitions．

    A company in California，US，has decided to offer online smells to people who visit its website．

    That is，if a pizza image comes on screen，your nose will catch the smell of bread and cheese！All you need to do is to connect a device（设备）called “iSmell” with your computer．This smart little device contains（包含）some chemicals that can create different kinds of smells．

    The company has invented software that changes the chemical composition（成分）of different smells into digital signals(数字信号）．An onscreen image，which is programmed with the proper digital signal，will start the“ iSmell" device．The device will use the software to change' the digital signal again and let go of the correct smell．This device reads the digital smell code（代码）from the website and creates the proper smell from its store of chemicals．This smell is then made to blow softly in the direction of the user with the support of a small fan．

    In order to let go of the correct smell，the company has created a “Scent Registry”，which contains a digital index of thousands of smells．The company plans to allow website developers to integrate（合成）the proper smells in digital code to their games and images．The company is also hoping that Hollywood filmmakers will use the smell technology in their movies．Imagine audiences getting the smell of rocket fuel as a spacecraft takes off on the cinema screen！Of course，filmmakers will have to be careful not to shoot in dirty neighborhoods，which have a lot of rubbish lying around．

    In most parts of the world, many students help their schools make less pollution．They join environment clubs．In an environment club, people work together to make our environment clean．

    Here are some things students often do．

    No-garbage lunches．How many lunch bags do you throw away after lunch? Environment clubs ask students to bring their lunches in bags that can be used again．Every week they will choose the classes that make the least garbage and report them to the whole school．

    No-car day．On a no-car day, nobody comes to school in a car including the students and the teachers．Cars give pollution to us, so remember:

    Walk, jump, bike, or run!

    Use your legs! It's lots of fun!

    Turn off the water! Do you know that some toilets can waste twenty to forty cubic meters of water an hour? In a year, that would fill in a small river. In the environment clubs, students mend those broken toilets．

    We love our environment．Let's work together to make it better．

      We are all busy talking about and using the Internet ,but how many of us know about the history of the Internet?

      Many people are surprised when they find that the Internet was set up in the 1960s.At that time, computers were large and expensive. Computer networks(网络)didn' t work well .If one computer in the network broke down, then the whole network stopped. So a new network system(系统) had to be set up. It should be good enough to be used by many different computers. If part of the network was not working, information could be sent through another part. In this way the computer network system would keep on working all the time. At first, the Internet was only used by the government, but, in the early 1970s, universities, hospitals and banks were allowed to use it too.

    However, computers were still expensive and the Internet was difficult to use. By the start of the 1990s, computers become cheaper and easier to use. Scientists had also developed software(软件) that made “surfing(浏览)” the Internet more convenient (方便).

    Today it is easy to get on-line and it is said that millions of people use the Internet every day. Sending e-mail is more and more popular among students.

   The Internet has now become one of the most important parts of people's life.

    Not many years ago, some farmers were worried because hawks ( 鹰) were taking many of their chicken. The farmers didn't know what to do. Finally they went to the country officials and asked for help.

    "Kill the hawks," the officials said. "We will even pay for them." So the farmers began to think of ways to kill the hawks.

    The farmers killed many hawks. They no longer had to worry about their chickens. But they now had a new worry. Field mice were eating up a lot of the farmers' grain.

    How did this happen?

    Hawks cannot only chickens but also field mice. They eat more field mice than chickens. But the farmers didn't know this. When they killed a lot of hawks, they changed the balance.

    When people move into a new place, they often destroy many wild plants. Often these plants are food for the animals. If the animals can't find enough plants to eat, they will starve or have to leave the place.

    In one part of the USA, for example, the deer there like to eat a certain kind of wild roses. The mountain lions there eat the deer. The number of deer, mountain lions and wild roses doesn't change much if people leave things as they are. But people killed many mountain lions in order to protect the deer. Soon there were so many deer that they ate up all the wild roses. Then the deer began to eat the green leaves of young trees. These trees were important to the farmers. So the farmers thought of ways to protect their trees. Now the deer had nothing to eat, and many of them died. This was another lesson from nature.

    To keep the balance of nature is important for us to remember.

    When you watch TV and play video games you make global warming(全球变暖) worse! To make electricity, fossil fuels(矿物燃料) are burned in big factories. But burning fossil fuels also makes greenhouse gases. This means that every time you use electricity you help make global warming worse!

    Cars are also making global warming worse. They burn fossil fuels in their engines, and send lots of greenhouse gases into the air.

    So what can we do to stop global warming?

    Try to use less electricity. First, turn off lights, your television, and your computer when you stop using them，You could also try to watch less TV. But you may find it hard to do these! Second, plant trees. Not only is it a fun thing to do, but it is also a great way to lower the number of greenhouse gases in the air. Trees take carbon dioxide(二氧化碳) out of the air when they grow. Last, don't throw away your rubbish, but try to recycle it. Because if rubbish is not recycled, it rots(腐烂) and makes a greenhouse gas called methane(甲烷). So try to recycle cans, bottles, plastic bags and newspapers. It'll make you feel great! And it'll help the Earth.

    Do stars only appear at night? The answer is no .Venus （金星） is the one and only star that can be seen in the daytime. It shone at its brightest in the night sky on February 17^th, 2017.

    Venus is the second planet from the sun in our solar system. It is the second brightest natural object, behind Earth's moon, in the night sky. Why is it so bright?

    First of all, Venus is the closest planet to Earth. It is also covered by highly reflective （反射的）clouds, which can reflect about 70 percent of the sunlight striking（照射） it, almost twice as much as Earth does.

    Some called 2017 the year of Venus, because the planet is at its brightest when it goes further away from the sun, and nearer to Earth. The brightest moment happened once in February, and happened again, during daylight, on April 30^th.

    If Venus is so bright and close to us, isn't it a better choice for human exploration than Mars? It is closer to Earth than Mars and it's closer to Earth in size. The closer distance to the sun means solar power would be easier to generate （产生） as well.

    However, with a temperature of about 465℃on the surface, Venus is the hottest planet in our solar system!

    But scientists never give up. Recently, a team of NASA and Russian scientists created new computer equipment that can stand the temperature of 480℃. It can work under Venus-like conditions for almost 22 days.

    The next step, according to the scientists, is to send a probe（探测器）to Venus by 2025.