When Melissa Mahan and her husband visited the Netherlands, they felt imprisoned by their tour bus. It forced them to see the city according to a particular route and specific schedule--but going off on their own meant missing out on the information provided by the guide. On their return home to San Diego, California, they started a new company called Tour Coupes. Now, when tourists in San Diego rent one of their small, brightly coloured three-wheeled vehicles, they are treated to a narration over the stereo system about the places they pass, triggered by Global Positioning System (GPS) satellite technology.
This is just one example of how GPS is being used to provide new services to tourists. "What we really have here is a technology that allows people to forget about the technology," says Jim Carrier of IntelliTours, a GPS tourism firm which began offering a similar service over a year ago in Montgomery, Alabama. The city is packed with sites associated with two important chapters in American history, the civil war of the 1860s and the civil-rights movement a century later. Montgomery has a 120-year-old trolley system, called the Lightning Route, which circulates around the downtown area and is mainly used by tourists. On the Lightning Route trolleys, GPS-triggered audio clips point out historical hotspots.
Other firms, such as CityShow in New York and GPS Tours Canada in Banff, Canada, offer hand-held GPS receivers that play audio clips for listening to while walking or driving. In South Africa, Europcar, a car-rental firm, offers a device called the Xplorer. As well as providing commentary on 2 000 points of interest, it can also warn drivers if they exceed the local speed limit.
If such services prove popular, the use of dedicated audio-guide devices could give way to a different approach. A growing number of mobile phones have built-in GPS or can determine their locations using other technologies. Information for tourists delivered via phones could be updated in real time and could contain advertisements. "Location-based services", such as the ability to call up a list of nearby banks or pizzerias, have been talked about for years but have never taken off. But aiming such services at tourists makes sense--since people are more likely to want information when in an unfamiliar place. It could give mobile roaming a whole new meaning.
In the opening paragraph, the author introduces his topic by （）
A. posing an illustration
B. justifying an assumption
C. making a comparison
D. explaining a phenomenon
参考答案：A
解析：
[直击题眼] 第二段开头：This is just one example of how GPS is being used…．
[深层剖析] 本题测试的是考生对文章第一段内容的理解及作者引出话题的手段。文章第二段开头明确表示这只是GPS提供新式旅游服务的一个范例。因此[A)正确。本选项的难点在于不少同学对[A]中的illustration理解不到位。除有“图表、插图”之意外，它还有“例证”之意，可视为example的同义词。
[主干扰项分析] 本文为信息传播型的文章，在第二段并未解释，而是又继续举例。(信息传播型文章的表达方式是事实多、细节详细、阅读时要尽量记忆各条信息，可以根据文章内容进行分析，提纲挈领地记住短文的中心思想。)因此[D]选项错误。
[次干扰项分析] [B]选项和[C]选项一般在科普性的文章中较为常见。