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    Pollution inside homes and other buildings kills more than 4 million people each year. Many people die as a result of breathing smoke or from cooking over wood-powered or coal-powered stoves.

    One way to reduce the number of deaths is through cooking equipment powered by the sun. Crosby Menzies, a solar power expert in a South African company, described his latest solar cooker called the "Sol-4". "It is four square meters of mirrors, six to eight meters in length. It is quite a large cooker. "

    The "Sol-4" works by reflecting (反射) light from the sun off large mirrors. The mirrors direct (把……对准) the light at a cooking pan. Then the light heats the pan with solar energy. Within two minutes, the pan is hot enough to cook sausages and onions. In just four minutes, water can be boiled. That is as fast as cooking with natural gas or electricity.

    The cooker is also much "friendlier" than other models because people do not have to stand in the sun to use it. And people can prepare meals without having to collect firewood or spend money on coal. Such individuals would be less likely to have breathing illnesses from harmful smoke.

    At present, the cooker only works when the sun is shining. But engineers are working on a way to make it work without sunlight.

    Each cooker costs about $ 2,000, which is a large amount of money for most Africans. To solve that problem, Crosby Menzies has created a non-governmental organization called Solar Cookers for Africa.  It plans to raise money through donations to provide poor people with solar cooking equipment.

    The world is not hungry, but it is thirsty. It seems strange that nearly 3/4 of the Earth is covered with water while we say we are short of（短缺）water. Why? Because about 97% of water on the Earth is sea water which we can't drink or use for watering plants directly(直接地）. Man can only drink and use the 3%-the water that comes from rivers and lakes. And we can't even use all of that, because some of it has been polluted(污染）.

    Now more water is needed. The problem is Can we avoid（避免）a serious water shortage later on? First, we should all learn how to save water. Secondly, we should find out the ways to reuse it. Scientists have always been researching in the field. Today, in most large cities water is used only once and then runs to the seas or rivers. But it can be used again. Even if(即使）every large city reused its water, there would not be enough. What can people turn to next?

    The seas seem to have the best answer. There is a lot of water in the seas. All that needs to be done is get the salt out of the sea water. This is expensive, but it's already used in many parts of the world. Scientists are trying to find a cheaper way of doing it. So you see, if we can find a way out, we'll be in no danger of drying up.

    Inventions usually make a big difference to people's lives. Do you have any great inventions at home? Do they help you a lot in your life or bring you much fun? Here are some of the most useful inventions in families according to a survey.

    Uber (优步)announced that it plans to invest 20 million in developing an aircraft in France over the next five years.

    It will open a new research and development center in Paris﹣its first technology hub outside of North America.

    "France is a perfect home for our next step forward with its strong history of research and development, world class engineers and a unique role in aviation (航空)worldwide,"Uber said in a statement.

    Uber already has R & D offices in Pittsburgh, Toronto, and San Francisco. They focus mainly on Uber's self﹣driving technology, but have also been working on Uber's Elevate flying car program.

    The Advanced Technologies Center in Paris will open later this year and only focus on flying cars. It will conduct research into airspace management, real﹣time communication networks, energy storage, and charging systems.

    Uber's announcement, made at a tech meeting in Paris, has been supported by French President Emanuel Macron, whose ambitious economic reforms are to attract more foreign investment.

    The company also announced a five-year research partnership with Ecole Polytechnique, a leading French institute of technology.

    Uber has been working on its flying car program since 2016. NASA became a partner for the program a year later by developing air traffic management for a fleet of flying cars.

    Uber expects flight to become a daily part of our transportation lives. The company believes it can offer rides in flying cars for about the same price as an Uber X ride. This technology may completely change our transportation lives in the future.

    Nowadays, computers and Internets are playing an important part in our life. Some people even say they can't live without them. We usually need to set passwords (密码) when we use computers and Internet. But not all the passwords are safe. In order to keep our accounts (账户)and personal information safe, we must learn how to make safe passwords.

    How can you make your computer and Internet passwords safe? Experts have some advice for you. You'd better remember the advice and they are useful for you. Here are the suggestions.

    Firstly, make your password out of capital(大写) letters. If your password is made of capital letters, it will be difficult for others to get into your account. It only takes a hacker(黑客) 10 minutes to work out a six- letter password made of small letters. But the same password in capital letters takes 10 hours to work out.

    Secondly, add numbers or symbols to your passwords. It may be much safer. Sometimes such password is not easy to remember, but it is really safe.

    Thirdly, never use personal information for passwords and use different passwords for different accounts. Experts say that a user should change his or her passwords every 90 days. In this way, hacker won't guess your passwords.