23. In which column of a newspaper can we read the passage?

A. Social news. B. Entertainment.

C. Technology. D. Education.

B

Automated cars-once a far­off dream-have in recent years left the field of science fiction and come closer to the American garage. Leading U．S.automakers say that real self­driving cars are coming within two decades and they're fighting to stay competitive.

These advances promise relief to people sick of two­hour driving and heavy traffic，but they leave open questions for a society shaped around the automobile for the past century. Perhaps no area is more uncertain than the environmental impact of automated vehicles. One report from the Department of Energy found that automated vehicles could reduce fuel consumption(油耗) for passenger cars by as much as 90%，or increase it by more than 200%.

That's a huge difference considering that more than a quarter of U．S. greenhouse gas emissions(排放) come from transportation，according to an expert. And scientists say reducing that figure will be the key to dealing with man­made climate change.

"There's a great energy influence possible，" says Jeff Gonde， a transportation researcher. "But there remains great uncertainty in the degree and even direction."

Depending on various factors，it remains to be seen how a future with automated cars will take shape. Most importantly，researchers expect that automated cars will lead to a sharp increase in the average miles traveled by a given vehicle. Key problems with driving a car，such as tiredness，age or drunkenness(醉酒)，will disappear，and car owners will be free to travel further and more frequently. Workers may choose to live even further away from the office，deciding to sleep in the car or use that time to work out in it. And，once in the city，car owners might guide their vehicles to drive around in circles rather than pay for parking.

"A lot of the uncertainty comes from not knowing how the value of people's time is going to change，" says Don MacKenzie，a researcher at the University of Washington. "There will be some kind of cost connected with the travel，but it's much less than it is today."

Researchers have tried to create a model of how humans might respond to automated driving using surveys，driving data and lab experiments，but eventually the great number of choices and assumptions involved in transportation has made reaching exact conclusions about driving behavior difficult.

Engineers say that the largely accident free vehicles can remove safety equipment，such as antilock brakes and airbags，which has increased the weight-and fuel consumption-of vehicles. Automated cars can also travel closer together，allowing them to take advantage of aerodynamics(气体力学)．Trucking fleets(车队) are already trying to take advantage of this fuel saving measure.