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

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

游客2023-07-29  27
问题     For centuries man dreamed of achieving vertical flight. In 400 A.D. Chinese children 【S1】______ with a fan-like toy that spun upwards and fell back to 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 【S2】______ and was never tested.
    The ancient dream was 【S3】______ realized in 1940 when a Russian immigrant, an aeronautical 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 【S4】______ . That vehicle was called a helicopter.
    Imaginations were fired. Men dreamed of commuting to work in their own personal helicopter. Every man would have one in his backyard. People anticipated that vertical flight transports would carry millions of 【S5】______ as do the airliners of today. Such 【S6】______ expectations were not fulfilled.
    The helicopter has now become an extremely versatile machine. It excels in military missions, carrying troops, guns and strategic instruments where other aircraft can not go. Corporations use them 【S7】______ airborne offices, many metropolitan areas use them in police work, construction and logging companies 【S8】______ 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 【S9】______ mission to a hard-to-get-to place is a likely task for a 【S10】______ . Among their other multitude of uses, they deliver people across town, fly to and from airports, assist in rescue work, and aid in the search for missing or wanted persons.

A) employ             B) passengers          C) as                D) helicopter
E) comfortable        F) earth               G) sufficient        H) urgent
I) disliked           J) played              K) finally           L) into
M) expected           N) fantastic           O) design [br] 【S2】
选项
答案 O
解析
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