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  3. Military drones already fly frequent missions and civilian operations using unmanned aircraft are coming. Drivcrlcss cars are cl

Military drones already fly frequent missions and civilian operations using unmanned aircraft are coming. Drivcrlcss cars are cl

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问题     Military drones already fly frequent missions and civilian operations using unmanned aircraft are coming. Drivcrlcss cars are clocking up thousands of test miles. So why not let remote-controlled ships set sail without a crew? Indeed, the maritime industry has started to think about what would be required to launch a latter-day Marie Celeste.
    Ships, like aircraft and cars, are increasingly controlled by electronic systems, which makes automation easier. The bridges of some modern vessels are now more likely to contain computer screens and joysticks than engine telegraphs and a giant ship’s wheel. The latest supply ships serving the offshore oil and gas industry in the North Sea, for instance, use dynamic positioning systems which collect data from satellites, gyrocompasses, and wind and motion sensors to automatically hold their position when transferring cargo to and from platforms, even in the heaviest of swells.
    However, as is also the case with pilotless aircraft and driverless cars, it is not so much a technological challenge that has to be overcome before autonomous ships can set sail, but regulatory and safety concerns. As in the air and on the road, robust control systems will be needed to conform to existing regulations.
    The maritime industry is interested in crewless ships for two reasons. The first is safety. Most accidents at sea are the result of human error, just as they are in cars and planes. So, if human operators are replaced by sophisticated sensors and computer systems, autonomous vessels should, in theory, make shipping safer.
    The second reason is, of course, cost. It is becoming increasingly difficult to sign up competent crew prepared to spend months away at sea. Moreover, some voyages are likely to get even longer for ships carrying non-urgent cargo. By some accounts, a 30% reduction in speed by a bulk carrier can save around 50% in fuel. This means slower steaming could provide big savings in fuel costs, but it would be at the expense of increased expenditure on crew for these longer voyages, both in wages and for the "hotel" facilities required on board. Removing the crew, though, also removes the need for their accommodation and its associated equipment, like heating and plumbing. And that provides room to carry more cargo.
In the first paragraph, unmanned aircraft is mentioned to______.
选项 A、serve as the topic of this text
B、introduce the topic of driverless cars
C、show the development of high-tech
D、introduce the topic of crewless ships
答案D
解析 文章从第二段开始都围绕crewless ships“无人轮船”在讨论，文章首段提到unmanned aircraft“无人机”和driverless cars“无人驾驶汽车”的目的仅仅是为了引出crewlessships的话题，故四个选项中，[D]为本题答案。
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