, by bike or by bus to save gas and emit (排放) less pollution into the air.7. Plant a tree: Help keep our air clean and make our world more beautiful.8. Don’t just sit there: “Everybody can be great ……

) and can help keep indoor air clean. In the new study, scientists observed four volunteers...自由基), which are formed from reactions between skin oils and ozone (臭氧) and can help keep indoor air ……

already export (出口) Swiss Alpine water, chocolate and cheese. Why not export our clean air too?” wrote...瑞士公司售卖阿尔卑斯山区空气。 You may buy bottled water from time to time. But will you buy bottled air?A Swiss ……

are at home, we need to clean our houses every day. At school, we must keep our classrooms clean and tidy... hours each night. We also need to get a lot of exercise and keep ourselves clean. Washing hands before ……

without crossing land. This makes it Earth’s cleanest air.“Our job is to find air as clean.... This makes it Earth’s cleanest air.“Our job is to find air as clean as you’re likely ……

the work.After that day, I knew how difficult it was to keep our school clean. We should never throw...打扫校园不简单。WE had a school clean-up activity last week.One of our duties (职责) was to clean ……

our bodies. Helium also helps cool satellites (卫星) and clean rockets (火箭).Helium is not toxic (有毒...共振成像机器) to see inside our bodies. Helium also helps cool satellites (卫星) and clean rockets (火箭 ……

Here are some numbers on our readers, about their rooms and how they keep them.Teens reader... to be interviewed.94% Have a room;78% Have a bookshelf70% Put posters on wall31% Clean their rooms ……

环卫工人们，你们辛苦了！THEY are people we often ignore – those who keep our streets clean each and every day. But they deserve (应得) our full respect.Sitting in your comfortable air-conditioned room, working ……

air comes in. This way, the walls help keep the air nice.Scientists in Switzerland (瑞士) have made... the air and let it go when fresh air comes in. This way, the walls help keep the air nice.VCGNew tech ……

in the bathroom is fresh.Keep yourgutters(水槽) clean and clear, so that dirty water doesn't make your...平常看起来干净舒适的家，竟然隐藏着这么多细菌！词数 223 建议阅读时间 5分钟THE smell of gas on the street may make many of us hold our ……

House plants (室内盆栽) help clean the air in our homes. They also make our homes lively (有生气的) and beautiful. But do you know how to care for them? For example, do you know how much sunlight (阳光 ……

clean. They also learn that our beautiful country can’t move forward in such a terrible environment...Several years ago, the sky was blue and clean. You could always see white clouds like cotton ……

it into the air, it cleans the air. There are small filters (过滤器) in it. It can take in bad air and put out clean air. ……

to be circulated (流通) every 2 hours. Open the window to let fresh air enter your room.● Keep the AC...In some places, there is no public heating system. People have to use the air conditioning (AC ……