共用题干 Rescue PlatformIn the aftermath of the terrorist attacks on the World Trade Center,security experts are trying to develop new ways of rescuing people from burning skyscrapers.One________(51)is a plat-form capable of flying vertically and hovering in the air_________(52)a helicopter. The plafform would rise up and down alongside a skyscraper and pick up people_________(53)in high stories。The idea for the vertical takeoff platform was hatched(策划)more than ten years ago by a Russian aerospace engineer,David Metreveli,who has since moved to Israel. Metreveli's design, _________(54)the Eagle,calls for two jet engines that_________(55)four large horizontal pro-pellers. The spinning of the propellers_________(56)the necessary lift,or upward force,to raise the platform. The more_________(57)is supplied to the propellers,the higher the platform _________(58).Moving the platform sideways involves_________(59)differing amounts of power to each propeller.Helicopters are now used in some________(60)to get people out of burning buildings.Es-cape baskets slung from them dangle beside the building for people to climb into._________(61),the baskets cannot reach every floor of a building_________(62)the ropes from which they hang become unstable_________(63)a certain length.So far,Metreveli has built a small-scale model of the Eagle to_________(64)his idea. In the wake of September 11,he has been able to secure enough funding to start building a larger ,4- meter by 4-meter prototype,_________(65)he calls the Eaglet. 51._________
A.idea B.skill C.building D.improvement正确答案A
