Directions: Fill in each blank with a proper word chosen from thebox. Each word can only be used once. Note that there is one word more than you need.

A. revolutionize       B. potential       C. unfold       D. convincing       E. handle F.competing       G. individually       H. vertically       I. stuck       J.multiple       K. adjust

How close are we to flying cars?

Even before George Jetson fascinated kids with his cartoon flying car, people dreamed of soaring above traffic congestion. Inventors and entrepreneurs have long tried and failed to make the dream a reality, but that may be changing.

Nearly a dozen companies around the globe, including some with deep pockets such as European aircraft maker to be the first to develop a new kind of aircraft that will enable commuters to glide above Airbus, are 【小题1】 crowded roadways. A few of the aircraft under development are cars with wings that 【小题2】 for flight, but most aren't cars at all. Typically they take off and land 【小题3】like helicopters. Rather than a single, large main rotor(旋翼), they have 【小题4】 small rotors operated by a battery - powered electric motor instead of a conventional aircraft engine.

It's no sure bet that flying-car dreams will turn into reality. There are many obstacles, including 【小题5】 regulators that the aircraft are safe, figuring out how to 【小题6】 thousands of new low-flying aircraft over cities without collisions and developing batteries that will keep them in the air long enough.

But entrepreneurs are moving forward. They see a vast 【小题7】 market for "air taxis" and personally owned small aircraft to transport people from the edges of metropolitan areas to city centers as urban areas grow more congested and people spend more time 【小题8】 in traffic. They envision tens of thousands of flying taxis delivering passengers to the rooftops of office buildings in city centers during rush hours.

"In as little as 10 years, products that 【小题9】 urban travel for millions of people could be on the market." said Zach Lovering, the leader of Aribus' project to develop an autonomous flying taxi. It's unclear yet how much the aircraft will cost, although prices are likely to vary significantly. Some of the aircraft are designed to be 【小题10】 owned, while others are more for commercial use. Designers hope that if demand is high, prices can be kept affordable through economies of mass production.