E

We already know the fastest, least expensive way to slow 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 age. 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 bending up even faster than predicted only a few years ago, and that the consequences could be severe if we don’t keep reducing emissions（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 emissions of CO2. We wanted to see how much we could cut back, so we went on a strict diet. The average US household（家庭）produces about 150 pounds of CO2 a day by doing common-place 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 emissions 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 emissions 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.

72. 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

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

A. freezing points B. burning points

C. melting points D. boiling points

74. It can be inferred from the passage that ________.

A. it is necessary to keep the air-conditioning on all the time

B. it seems possible for every household to cut emissions of CO2

C. the average US household produces about 3,000 pounds of CO2 a month

D. the average European household produces about 1,000 pounds of CO2 a month