Save the world's trees

    "When it comes tothe Earth, there is no time to waste." says the Earth Day Network. And that isright. Protecting our environment is very important, and World Earth Day wascreated in 1970 to ask more people to protect our environment. On April 22, peoplearound the world celebrate Earth Day.

Every year thereis a special topic, and this year it is "Trees for the Earth", so Earth Daythis year will be all about planting trees. They are planning to plant 7.8billion trees within the next five years.

That's a biggoal, and you might wonder why trees are so important. Because they can take incarbon dioxide (CO₂) and protect the air quality(质量). CO₂ isa chemical in our atmosphere, but humans make too much of it. Each person makesabout 2.3 tons a year, which is bad for the environment.

Well guess what!Planting new trees is important because people cut down a huge number of trees.Last year, there were 3 trillion trees in the world, about 139 billion inChina. But according to China Daily, the world's total number has been almostcut in half since human civilization(文明) began. That's because 15billion trees are cut down every year.

So we need toplant more to make up for（弥补）the ones we lost. One treecan take in 21. 8 kilograms of CO₂ per year. And it's still one ofthe cheapest and best ways to get rid of CO₂.

    But don't forget that we can also help the environment by cutting down on how much energy(能源) or water we useevery day. Every little thing helps.

根据短文内容，回答问题（1-4），英译汉（5）。

    Some of the greatest problems we face today are the destruction (破坏) of our environment. Brown clouds, polluted water, endangered wild animals.., these problems seem so huge.

    So my family does what we can. We take cloth bags to stores instead of using plastic bags. We walk where we don't have to drive...

    But does it do any good? When I am the only one in line at the market with cloth bags, am I doing any good? Does my walking to stores make any real difference to the world?

    I recently learned something about flamingos (火烈鸟) which like to get together in groups of a thousand or more. Every year, when the time comes for migration (迁徙), a few of them first takeoff from the lake. But none of the others seem to notice, so the small group returns. However, the next day they try again. This time few more fly along with them, but most of them still pay no attention, so they return again. They try for several times. Every time a few more birds join in but, since the thousands of others still take no notice, the great migration plan is once more stopped.

    Then one day something changes. The same small group of birds once again starts flying and a small number more join in just as before, then more. Finally, they all take flight and the migration really begins. What a spectacular sight it must be—thousands of flamingos taking off into the sky at once!

    A few can make a difference. Even if you're the one to take the first step, and continue trying, others will someday take notice and together we will solve even our greatest problems.

    Is there intelligent（有智力的）life on other planets? For years, scientists said "no." or "we don't know." But today this is changing. Seth Shostak and Alexandra Barnett are astronomers（天文学家）. They believe intelligent life exists（存在）somewhere in the universe. They also think we will soon contact them.

    Why do Shostak and Barnett think intelligent life exists on other planets? The first reason is time. Scientists believe the universe is about 12 billion years old. "This is long enough for other planets to have intelligent life, "say Shostak and Barnett. The second reason is size the universe is huge. "Tools like the Hubble Telescope（哈勃望远镜）have shown that there are at least 100 billion galaxies, "says Shostak. "And our galaxy, the Milky Way, has at least 100 billion stars. Some planets going around these stars might be similar to the earth. "

    In the past, it was hard to look for signs of intelligent life in the universe. But now, powerful telescopes（高倍望远镜）allow scientists to discover smaller planets-the size of Mars or the earth-in other solar systems, these planets might have intelligent life.

    Have beings from space already visited the earth? "Probably not, "says Shostak. "It's a long way away. However, intelligent beings may contact us in other way, such as radio signals（信号）. In fact, they may be trying to communicate with us now, but we don't have the right tools to receive their messages. However, this is changing. By 2025, we could make contact with other life forms in our universe and we might help each other. "

    Robots seem very new to most people. But they have a long history. The first one was made by a Greek inventor. You may have seen robots in some films. The robots in these films are stronger, faster and more clever than people in real life. Most robots are used in factories. They are used to do many dangerous, difficult or boring jobs. Some people can't look after themselves and move around. They need dogs to help them. These dogs are called guide dogs. Scientists are making robot dogs to help them. In the future, robot dogs might take the place of these guide dogs.

    Robots are also used in American hospitals. At one hospital, a robot takes meals from the kitchen to the sick people's rooms,   it never loses its way because it has a map of the hospital in its computer system.

    In the future, robots will work in space. But robots will never take the place of human beings, though they can help us in a lot of different ways.