A、Mechanical failure. B、Heavy traffic. C、Extreme weather. D、Human error. D录音提到，专家指出在每年120万的道路死亡人数中，90％都是由人的过错造成的。因此本题选D项。A项“机械故障

This summer, the latest version of Google’s self-driving car will make its first appearance on public roads. The two-seat vehicle does not need a gas pedal or steering wheel. The prototype can drive, brake and recognize road dangers without human involvement. Google says the car is the first vehicle built for the purpose of self-driving.
    However, the new vehicle is not designed for long trips. It does not have air bags or other safety devices required by the federal government. It cannot go more than 40 kilometers per hour. The vehicle is electric and has to be recharged after 130 kilometers. And it can only drive in areas that have been thoroughly mapped by Google.
    Google will first build and test 25 driverless vehicles in areas around the company’s headquarters in Mountain View, California. Then, the company plans to build more and expand testing to areas that have more hills and more rain.
    Sergey Brin is a co-founder of Google. He says the computer-controlled cars can eliminate, or end, driving mistakes made by humans. Experts say 90 percent of the 1.2 million yearly road deaths are caused by human error. Self-driving cars could also improve areas of high traffic and especially help older people and disabled people.
    Google first announced that it was working on a driverless car in 2010. Mr. Brin says Google does not want to be a car company, but wants automakers to use its technology.
    Critics worry about the safety of having cars without human drivers. And, Google admits there have been minor accidents in the six years it has been testing autonomous cars.
    Critics also question the dependability of self-driving cars. They wonder if the cars can be trusted to work all the time. They also ask if such cars appeal to people.
    In 2013, J.D. Power and Associates did a study of U.S. drivers. It found that only one in five was interested in a fully autonomous car.
    Mr. Urmson says Google needs to do a better job of educating people about self-driving technology. He also says Google needs to better inform the public about its progress with the technology.
    Google is not the only company developing self-driving cars. Mercedes-Benz, Inflniti and others already have highly developed driver assistance systems that require little help from a driver. But other automakers think self-driving cars will be made available feature-by-feature instead of all at once. They say this gives people time to adapt to self-driving technology.
    Mr. Brin says Google is still improving its plans for self-driving cars, but he’s excited about their possibility.
    Google hopes to have its driverless cars available in the next five years.
    19. What do we learn about the latest version of Google’s self-driving cars?
    20. What is the primary reason for road deaths?
    21. What did Power and Associates’ study of U. S. Drivers show?
    22. What do we learn about Google?