题目内容：

阅读理解。

We already know the fastest,least expensive way to slow down climate change:use less energy.With a little effort,and not much money,most of us could reduce our energy diets by 25 percent or more—doing the Earth a favor while also helping our wallets.

Not long ago,my wife,PJ,and I tried a new diet—not to lose a little weight but to answer an annoying question about climate change.Scientists have reported recently that the world is heating up even faster than predicted only a few years ago,and that the consequences(后果)could be severe if we don’t keep reducing emission(排放)of carbon dioxide(CO2)and other greenhouse gases that are trapping heat in our atmosphere.

We decided to try an experiment.For one month we recorded our personal emission of CO2.We wanted to see how much we could cut back,so we went on a strict diet.The average US household produces about 150 pounds of CO2 a day by doing common things like turning on air conditioning or driving cars.That’s more than twice the European average and almost five times the global average,mostly because Americans drive more and have bigger houses.But how much should we try to reduce?

For an answer,I checked with Tim Flannery,author of The Weather Makers:How Man Is Changing the Climate and What It Means for Life on Earth.In his book,he had challenged readers to make deep cuts in personal emission to keep the world from reaching extremely important tipping points,such as the melting(融化) of the ice sheets in Greenland or West Antarctica.“To stay below that point,we need to reduce CO2 emission by 80 percent,”he said.

Good advice,I thought.I’d opened our bedroom windows to let in the wind.We’d gotten so used to keeping our air-conditioning going around the clock.I’d almost forgotten the windows even opened.We should not let this happen again.It’s time for us to change our habits if necessary.

1.Why did the author and his wife try a new diet?

A.To take special kinds of food.

B.To respond to climate change.

C.To lose weight.

D.To improve their health.

2.The underlined words“tipping points”most probably refer to “   ”.

A.freezing points               B.burning points

C.melting points                D.boiling points

3.According to the passage,Tim Flannery   .

A.made deep cuts in his personal emission of CO2

B.wrote a book about the climate changes

C.succeeded in reducing CO2 emission by 80 percent

D.was an author popular among readers

4.Which of the following would be the best title for this passage?

A.Saving Energy Starts at Home

B.Changing Our Habits Begins at Work

C.Changing Climate Sounds Reasonable

D.Reducing Emission of CO2 Proves Difficult