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  3. For centuries men dreamed of achieving vertical flight. In 400 A. D. Chinese

For centuries men dreamed of achieving vertical flight. In 400 A. D. Chinese

游客2024-03-01  63
问题     For centuries men dreamed of achieving vertical flight. In 400 A. D. Chinese children played with a fan-like toy that spun upwards and fell back to the earth as rotation ceased. Leonardo da Vinci conceived the first mechanical apparatus, called a "Helix", which could carry a man straight up, but this was only a design and was never tested.
    The ancient dream was finally realized in 1940 when a Russian engineer piloted a strange looking craft of steel tubing with a rotating fan on top. It rose awkwardly and vertically into the air from a standing start, hovered a few feet above the ground, went sideways and backwards, and then settled back to the earth. That vehicle was called a helicopter.
    Imaginations were fired. Men dreamed of going to work in their own personal helicopters. People anticipated that vertical flight transports would carry millions of passengers as do the airliners of today. Such fantastic expectations were not fulfilled.     The helicopter has now become an extremely useful machine. It excels in military missions, carrying troops, guns and strategic instruments where other aircraft cannot go. Corporations use them as airborne offices, many metropolitan areas use them in police work, construction and logging companies employ them in various advantageous ways, engineers use them for site selection and surveying; and oil companies use them as the best way to make offshore and remote work stations accessible to crews and supplies. Any urgent mission to a hard-to-get-to place is a likely task for a helicopter. Among their other multitude of uses: deliver people across town, fly to and from airports, assist in rescue work, and aid in the search for missing or wanted persons. [br] Under which of the following conditions are helicopters found to be absolutely essential?
选项 A、For extremely high altitude flights.
B、For urgent mission to places inaccessible to other kinds of craft.
C、For rescue work.
D、For high-speed transportation.
答案 B
解析 关键要注意题目中的“absolutely essential”，文章中第四段提到直升飞机的许多用途，比如可以当作空中办公室(airborne offices)，都市里警方用来执行各种任务，直升飞机也可以帮助建筑工人和伐木工人等，但直升飞机最大的用武之地还是“到其他类的飞机难以到达的地方执行任务”。因此，正确答案是B项。
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