We can all contribute to a greener world．Just follow these ten golden rules:
●Stop getting junk mail．Billions of junk mail can be sent every year．Half of it is never opened．Get-your name off mailing lists．If 100,000 people stopped getting junk mail today, it would save 150,000 trees a year．
●Stop reading newspapers．All over the world, millions of newspapers are thrown away every day, 44 million newspapers in the USA alone —that's half a million trees a week．Either recycle your newspapers or read the hews online．
●Buy clothes made from organic materials．Conventional cotton farming seriously pollutes the environment, most of which uses chemical pesticides （农药） and fertilizers． Organic is better!
●Switch to solar energy．In one day, the sun will provide enough energy to power the planet．Why aren't we using it?
●If you have to drive, share the ride．Most cars in the USA have only one occupant．Also, 25 percent of car rides are less than 1．5 kilometres．Get out and walk!
●Unplug your PC, TV and VCR．Simply turning them off isn't enough．Sets left on standby are still using 25 percent of their power．
●Hold on to your balloons．Helium-filled balloons which fly away usually end up in a lake or river, where they can choke aquatic (水生的) creatures．Save your balloons and use them again．Or better still, don't use them at all．
●Feed the birds．Wild birds need food, especially in v/inter when other sources can be scarce．The greater the range of foodstuffs you put out for them, the more types of birds you will attract．
●Plant a garden at your school．Learn the connection between the land and the table．Plant vegetables to eat, flowers to admire and trees to improve the air．
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What is the main purpose of the passage?

A．To provide some health advice on how to work．

B．To suggest some ways how to make full use of solar energy．

C．To advise protecting environment and saving energy．

D．To advise on how to recycle waste and save energy．

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．The underlined expression "left on standby" in the sixth rule means__   __．

A．ready to start and use electricity	B．ready to be turned off
C．ready to be repaired	D．ready to be．put away

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．Which of the following will NOT protect trees from being cut down to make paper?

A．Not buying newspapers．	B．Don't accept junk mail．
C．Read your newspaper online．	D．Read only one newspaper．