英语阅读理解2For centuries man had dreamed of achieving vertical f

英语阅读理解2
For centuries man had dreamed of achieving vertical flight.In 400 A.D.Chinese children played 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 “Helix”,which could carry a man straight up but this was only a design and never tested.
The ancient dream was finally realized in 1940 when a Russian immigrant,an aeronautical engineer,piloted a strange-looking craft of steel tube 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 commuting to work in their personal helicopter.Every man would have one in his backyard.People anticipated that vertical flight transports would carry millions of passengers as the airlines of today do.Such fantastic expectations were not fulfilled.
The helicopter has now become an extremely versatile machine.It excels in military missions,carrying troops,guns and strategic instruments to places where other aircrafts 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 likely a task for a helicopter.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.
11.What is a helicopter?
A.An aircraft that can go faster than the ordinary airplane.
B.An aircraft that fits into the smallest possible place.
C.An aircraft that can fly up vertically
D.An aircraft that is used only for commercial service.
12.What is said about the development of the helicopter?
A.Helicopters have only been worked on by man since 1940.
B.An Englishman was the first to achieve flight in a helicopter.
C.Helicopters were considered more dangerous than the early airplane.
D.Some people thought they would become widely used by the average individual.
13.Under what condition are helicopters found to be almost indispensable?
A.For overseas passenger transportation
B.For extremely high altitude
C.For high speed transportation
D.For urgent missions to inaccessible places
14.What principle do helicopters work on?
A.Combination of propellers in front and on top.
B.A propeller on top.
C.One propeller in the center of the aircraft and others at each end
D.A propeller underneath for lifting power