题目内容
（请给出正确答案）
Jet belts and rocket belts were developed ______.
A．20-30 years ago
B．50 years ago
C．recently
D．30 years ago
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更多“Jet belts and rocket belts wer…”相关的问题
Proponents of seat belts on school buses believe that______.
A．the use of seat belts can stop the death and injury
B．seat belts can make children quiet when the bus driver is working
C．seat belts can help children realise the importance of using them in moving vehicles
D．seat belts can teach children lessons about the importance of keeping away from drivers
-- Seat belts save lives.--().
A.I won’t put on my seat belts.
B.I will put on my seat belt.
C.It’s sure.I agree.
A.fast
B.tight
C.fastened
D.tense
The Solo Trek had a 120 horsepower engine with twin fans. Only one person flies. As you fly above the roofs, you lean a little forward. You can see everything under you. You are flying like Superman.
Michael Moshier looked at the jet belt and the rocket belt that was developed 20, 30 years ago. Nothing ever came from them. People still can't fly.
Inventors have tried to make it easy for people to fly. Paul Moiler has been working on his flying car for 30 years. He now says it is ready for tests. It would take off and land vertically, go 600 miles an hour, and deliver 20 miles to the gallon. A computer would do the actual flying. He says it could be sold next year for about a million dollars.
NASA is working with Moshier to help develop his flying machine. The first users are likely to be military.
It's been 50-years since Robert Fulton invented his airphibian, a flying car. It flew, and is now in the Smithsonian Museum.
Getting dreams to fly is never easy.
The Solo Flyer is able to lift off the ground by using ______.
A．a solar powered engine
B．engine-powered twin fans
C．large flapping wings
D．rotating blades
A、I like it very much.
B、Never mind.
C、That isn't very expensive.
D、I really like this blue one、In fact, it's my favorite among the belts here.
ir complex ecology, naming, classification, and mapping have also become more particular, stressing what was actually present rather than postulating about climatic potential.
［B］ In regions of higher rainfall, such as eastern Africa, savanna vegetation is maintained by periodic fires. Consuming dry grass at the end of the rainy season, the fires burn back the forest vegetation, check the invasion of trees and shrubs, and stimulate new grass growth.
［C］ Once, as with the scientific treatment of African soils, a much greater uniformity was attributed to the vegetation than would have been generally accepted in the same period for treatments of the lands of western Europe or the United States.
［D］ The vegetational map of Africa and general vegetation groupings used here follow the White map and its extensive annotations.
［E］ African vegetation zones are closely linked to climatic zones, with the same zones occurring both north and south of the equator in broadly similar patterns. As with climatic zones, differences in the amount and seasonal distribution of precipitation constitute the most important influence on the development of vegetation.
［F］ Nevertheless, in broad terms, climate remains the dominant control over vegetation. Zonal belts of precipitation, reflection latitude and contrasting exposure to the Atlantic and Indian oceans and their currents, give some reality to related belts of vegetation.
［G］ The span of human occupation in Africa is believed to exceed that of any other continent. All the resultant activities have tended, on balance, to reduce tree cover and increase grassland; but there has been considerable dispute among scholars concerning the natural versus human-caused development of most African grasslands at the regional level.
Why does the author mention the Massachusetts Bay Colony？
A．It was the headquarters of the United States Lighthouse Board.
B．Many of the tallest lighthouses were built there.
C．The first lantern wicks were developed there.
D．The first lighthouse in North America was built there.
A．Once college graduates take a temporary job, they soon become used to it.
B．College graduates have developed the habit of taking temporary jobs.
C．Many college graduates might never find jobs for which they were trained.
D．More and more college graduates are unwilling to change their jobs.
The passage mainly tells us that ______.
A．the sense of trust is the first part of healthy personality to be developed
B．the sense of trust is an early-formed and important element in the healthy personality
C．trust can exist only in relation to other stages of growth
D．individuals with psychopathic personalities were usually unloved in infancy and have no sense of trust
According to preliminary market surveys, there are 10,000 would-be space tourists willing to spend $1 million each to visit the final frontier. Space Adventures in Arlington have taken more than 130 deposits for a two-hour, $98,000 space tour tentatively set to occur by 2005. This may sound great, but there are a few hurdles: Putting a simple satellite into orbit--with no oxygen, lift: support or return trip necessary—already costs an astronomical $2,200/kg. And that doesn't include the cost of insuring rich and possibly litigious (爱打官司的) passengers. The entire group of entrepreneurs trying to comer the space- tourism market has between them "just enough money to blow up one rocket".
The U.S. space agency has plenty of money but zero interest in making space less expensive for the little guys. So the little guys are racing to do what the government has failed to do: design a reusable launch system that's inexpensive, safe and reliable. Kelly Space's prototype looks like a plane that has sprouted rocket engines. Rotary Rocket in California has a booster with rotors to make a helicopter-style. return to earth. The first passenger countdowns arc still years away, but bureaucrats at the Federal Aviation Administration in Washington arc already informally discussing flight regulations. After all, you can't be too prepared for a trip to that galaxy far, far away.
Which of the following is the best title for the passage？
A．Take Vacations in Space
B．Building Hotels in Space
C．Flight Regulations in Space Travels
D．Cost of Space Traveling
