You can be proud of yourselves, even if you can only make one or two of these green changes. The goal here is to limit carbon dioxide and other greenhouse gases, which are closely connected to the big problem of global-warming (全球变暖).

    WAY 1: Bring your own cup to Starbucks. You'll get a 10-cent discount, and it's one less paper cup to end up in a dustbin. The store won't create more waste when they throw away a cup.

    WAY 2: Turn off your computer. When in standby mode, your PC is still using energy. Turning off a monitor (显示器) for 40 hours a week may only save $ 5 a month, but it reduces CO₂ by 750 pounds.

    WAY 3: Reuse plastic bags. Instead of throwing away 100 billion plastic bags a year, try and get a second, third, or tenth use out of them. Better yet, next time you shop, try a reusable bag. The amount of oil it would take to make just 14 plastic bags would run your car for one mile.

    WAY 4: Use recycled paper in the bathroom. Most of the toilet paper we use is made from trees found in forests. If every family replaced(替换)one roll of toilet paper with a recycled one, 424,000 trees would still be standing.

    WAY 5: Plant a tree. Adding green to your garden is beautiful and earth-pleasing. Just one tree will help make cleaner air and save the environment from 5, 000 pounds of hot carbon dioxide each year.

    We know the mosquito very well. Mosquitoes fly everywhere. They can be found almost all over the world， and there are more than 2，500 kinds of them.

    No one likes the mosquito. But the mosquito may decide that she loves you. She？ Yes，she. It's true that male mosquito doesn't bite（咬） and only the female mosquito bites because she needs blood to lay eggs. She is always looking for things or people she wants to bite. If she likes what she finds， she bites. But if she doesn't like your blood，she will turn to someone else for more delicious blood. Next time a mosquito bites you，just remember you are chosen. You're different from the others！

    If the mosquito likes you，she lands on your body without letting you know. She bites you so quickly and quietly that you may not feel anything different. After she bites，you will have an itch（痒） on your body because she puts something from her mouth together with your blood. By the time the itching begins，and she has flown away.

    And then what happens？ Well，after her delicious dinner，the mosquito feels tired. She just wants to find a place to have a good rest. There，on a leaf or a wall， she begins to lay eggs，hundreds of eggs.

    Clothes are traditionally made of natural materials, such as cotton, leather and wool. They are all from plants or animals, but that doesn't mean they're friendly to the earth. For example, farmers have to use a lot of chemicals to grow cotton plants.

    Scientists are now looking for new ways to make clothing materials. They hope the new materials are both comfortable and good for the earth. Scientists have worked out how to make materials out of corn husks(棉籽), chicken feathers and rice straws.

    "They used to be useless things. We always have a problem of how to deal with them," Yang, a scientist says, "Now, we can turn them into beautiful materials. Chicken feathers are better than other things. They have small air pockets like honeycombs. That means it will be very warm if you use them to make a jacket or sweater, and I think more and more people will like to buy these kinds of clothes."

    Is there intelligent(有智力的) life on other planets(行星)? 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 somewhere in the universe. They also think we will soon contact these beings(人；生物).

    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 (银河系) ," says Shostak. "And our galaxy, the Milky Way, has at least 100 billion stars. Some planets going around these stars might be similar to 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 Earth--in other solar systems (太阳系).These planets might have intelligent life.

    Have beings from space already visited 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.

    Populations of white-tailed deer (白尾鹿) are growing rapidly in many parts of the United States. As populations grow, food becomes a problem. Many deer die of hunger. Others grow up small and unhealthy. In search of food, hungry deer move closer to where humans live. They eat farm crops, vegetables and even trees. Besides, increased numbers of deer near roads can cause traffic accidents.

    People admire the grace and fast speed of deer. Most people don't want these animals to be hungry and ill. Should people take action to control the growing deer populations?

Should People Take Direct Action?

    Many people think that hunting (打猎) is the best way to control the animal populations. Wildlife managers will see if there's enough food in an area and decide its carrying capacity (容量). Then hunters with licenses are sent to help control the number of deer. Hunting is usually not allowed in cities or suburbs, however.

    Some people have the idea to catch the deer and move them to other places. But this method is expensive and requires finding another place that can accept the deer without breaking the balance of ecosystem.

    Scientists are also working to develop chemicals to control the birth rate in deer populations. But this plan works for only one year at a time.

Should People Take Indirect Action?

    Some suggest bringing in natural enemies of deer, such as wolves, lions and bears, to areas with too many deer. But these animals could also hurt dogs, cats, and even humans. Other communities have built tall fences (篱笆) around areas to keep out the deer. However, this is impossible for farmers.

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    Some people are against any kind of action. They support leaving the deer alone. Animal populations in an area naturally go up and down over time. Doing nothing means that some deer will die of hunger or illness. But finally, the population will reach a size within the carrying capacity of the environment. So, let nature go its own way.