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.

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. 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

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