阅读下面短文，并按照题目要求用英语回答问题。

     LONDON/SAN FRANCISCO-The Sydney Opera House to San Francisco's Golden Gate Bridge went

dark as people switched off lights in their homes and skylines dimmed around the world on Saturday to

show concern about global warming.

     Up to 30 million people were expected to have turned off their lights for 60 minutes by the time "Earth

Hour"-which started in Suva in Fiji and Christchurch in New Zealand-completed its cycle westward. More

than 380 towns and cities and 3 500 businesses in 35 countries signed up for the campaign that is in its

second year after it began in 2007 in Sydney, Australia's largest city.

     "Earth Hour shows that every day people are prepared to pull together to find a solution to climate change.

It can be done." said James Leape of WWF International, which was running the campaign.

     Lights at Sydney's Opera House and Harbour Bridge were lowered as Australians held candle-lit beach

parties, played poker by candlelight and floated candles down rivers.

     In Bangkok, some of the city's business districts, shopping malls and billboards went dark, although street

lights stayed on. One major hotel invited guests to dine by candle light and reported brisk business.

     In Copenhagen, the Tivoli Gardens and the Royal Palace and the opera darkened for an hour, along with

many street lights.

     "In the central square a lot of people were standing looking at the stars," said Ida Thuesen, spokeswoman

for WWF Denmark. "It's not often you can see the stars in a city."

     "It is not just about turning off the lights, it is about raising awareness," San Francisco Mayor Gavin

Newsom said. "Energy efficiency is low-hanging fruit. Energy efficiency is the easiest thing we can do to

reduce global warming."

     Buildings account for about one-third of the carbon emissions that scientists say will boost global average

temperatures by between 1.4 and 4.0 degrees Celsius this century, bringing floods and famines and putting

millions of lives at risk. Organizers of Earth Hour said that while switching off a light for one hour would

have little impact on carbon emissions, the fact that so many people were taking part showed how much

interest and concern about the climate crisis had taken hold. They said they planned a similar event March

28, 2009.

1. What's the main idea of the first paragraph? (No more than 15 words.) 

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2. According to the passage, what does this activity "Earth Hour" indicate? (No more than 15 words.) 

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3. What does the underlined words "account for" mean in English? (No more than 7 words.) 

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4. What's the purpose of writing this passage? (No more than 5 words.)

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5. What do you think of "Earth Hour"? (No more than 20 words) 

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