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  3. The car, and the roads it travels on, will be revolutionized in the twenty first century. The key to tomorrow’s "smart cars" wil

The car, and the roads it travels on, will be revolutionized in the twenty first century. The key to tomorrow’s "smart cars" wil

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问题     The car, and the roads it travels on, will be revolutionized in the twenty first century. The key to tomorrow’s "smart cars" will be sensors. "We’ll see vehicles and roads that see and hear and feel and smell and talk and act," predicts Bill Spreitzer, technical director of General Motors Corporation’s ITS program, which is designing the smart car and road of the future.
    Approximately 40, 000 people are killed each year in the United States in traffic accidents. Fully half of these fatalities come from drunk drivers, and many others from carelessness. A smart car could eliminate most of theses car accidents. It can sense if a driver is drunk via electronic sensors that can pick up alcohol vapor in the air, and refuse to start up the engine. The car could also alert the police and provide its precise location if it is stolen.
    Smart cars have already been built which can monitor one’s driving and the driving conditions nearby. Small radars hidden in the bumpers can scan for nearby cars. Should you make a serious driving mistake, the computer would sound an immediate warning.
    At the MIT Medial Lab, a prototype is already being built which will determine how sleepy you are as you drive, which is especially important for long-distance truck drivers. The monotonous, almost hypnotic process of staring at the center divider for long hours is a grossly underestimated, life-threatening hazard. To eliminate this, a tiny camera hidden in the dashboard can be trained on a driver’s face and eyes. If the driver’s eyelids close for a certain length of time and his or her driving becomes erratic, a computer in the dashboard could alert the driver.
    Two of the most frustrating things about driving a car are getting lost, and getting stuck in traffic. While the computer revolution is unlikely to cure theses problems, it will have a positive impact. Sensors in your car tuned to radio signals from orbiting satellites can locate your car precisely at any moment and warn of traffic jams. We already have twenty-four Navstar satellites orbiting the earth, making up what is called the Global Positioning System. They make it possible to determine your location on the earth to within about a hundred feet. At any given time, there are several GPS satellites orbiting overhead at a distance of about 11,000 miles. Each satellite contains four "atomic clocks" , which vibrate at a precise frequency, according to the laws of the quantum theory.
    As a satellite passes overhead, it sends out a radio signal that can be detected by a receiver in a car’s computer. The car’s computer can then calculate how far the satellite is by measuring how long it took for the signal to arrive. Since the speed of light is well known, any delay in receiving the satellite’s signal can be converted into a distance. In Japan there are already over a million cars with some type of navigational capability.(Some of them locate a car’s position by correlating the rotations in the steering wheel to its position on a map)
    With the price of microchips dropping so drastically, future applications of GPS are virtually limitless, " The commercial industry is poised to explode," says Randy Hoffman of Magellan Systems Corp. which manufactures navigational systems. Blind individuals could use GPS sensors in walking sticks, airplanes could land by remote control, hikers will be able to locate their position in the woods— the list of potential uses is endless.
The word "it" in the passage refers to______.
选项 A、a drive
B、smart car
C、sensor
D、car accident
答案B
解析 考查代词指代。根据代词与被指代名词单复数一致且搭配合理的原则，“A smartcar could eliminate most of theses car accidents．It can sense if a driver is drunk via…”中，it应指代“a smart car”。故选B。
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