首页
登录
职称英语
For centuries men dreamed of achieving vertical flight. In 400 AD Chinese ch
For centuries men dreamed of achieving vertical flight. In 400 AD Chinese ch
游客
2023-07-27
13
管理
问题
For centuries men dreamed of achieving vertical flight. In 400 AD Chinese children played with a fanlike 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 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 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 airlines 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 what conditions are helicopters found to be absolutely essential?
选项
答案
Helicopters are essential for any urgent mission.
解析
从最后一段倒数两句话可看出,在很多紧急情况下而人类又很难到达的地方,直升机的使用是必需的。
转载请注明原文地址:https://tihaiku.com/zcyy/2873764.html
相关试题推荐
1.入学条件2.学费和奖学金3.住宿情况DearSirorMadam,IamaChinesestudentwhowish
[originaltext]M:Carol,doyouknowwhenProf.Wang’sChineseLiteratureFinal
[originaltext]M:Carol,doyouknowwhenProf.Wang’sChineseLiteratureFinal
ThreecenturiesagotheFrenchmathematicianReneDescartespredictedthati
ThreecenturiesagotheFrenchmathematicianReneDescartespredictedthati
ThreecenturiesagotheFrenchmathematicianReneDescartespredictedthati
Forcenturiesmendreamedofachievingverticalflight.In400A.D.Chinese
Inthelatenineteenthandearlytwentiethcenturies,oneofthemostclearl
Inthelatenineteenthandearlytwentiethcenturies,oneofthemostclearl
Inthelatenineteenthandearlytwentiethcenturies,oneofthemostclearl
随机试题
______theircommercialrivals,thecompanyhasmadebigprofitsthisyear.A、Ali
ThemoreIreflectonthe23impressiveyearssincethesigningoftheMont
TherailroadsplayedakeyroleinthesettlementoftheWest.Theyprovided
(Ⅰ)证明拉格朗日中值定理:若函数f(x)在[a,b]上连续,在(a,b)内可导
躯体运动受中枢神经系统调控,控制随意运动的最高级中枢位于()。A.大脑 B
小儿营养性缺铁性贫血的临床表现及实验室检查,下列错误是A.呈大细胞性贫血 B.
有中枢抑制作用的M胆碱受体阻断药是A.阿托品B.后马托品C.山莨菪碱D.溴丙胺太
非程序化决策:指管理者在计划管理中对不经常出现的新问题所进行的非常规的决策。根据
下列说法中,正确的是( )。A.大赦既赦其刑,又赦其罪B.特赦只赦其刑
(2020年真题)根据《中华人民共和国个人所得税法》,有下列情形之一的,纳税人应
最新回复
(
0
)