单选题
Flying the Hypert Skies

A little airplane has given new meaning to the term "going hyper."
The Hyper-X recently broke the record for air-breathing jet planes when it traveled at a hypersonic speed of seven times the speed of sound. That's about 5,000 miles per hour. At this speed, you'd get around the world -- flying along the equator -- in less than 5 hours.
The Hyper-X is an unmanned, experimental aircraft just 12 feet long. It achieves hypersonic speed using a special sort of engine known as a scramjet. It may sound like something from a comic book, but engineers have been experimenting with scramjets since the 1960s.
For an engine to burn fuel and produce energy, it needs oxygen. A jet engine, like those on passenger airplanes, gets oxygen from the air. A rocket engine typically goes faster but has to carry its own supply of oxygen. A scramjet engine goes as fast as a rocket, but it doesn't have to carry its own oxygen supply. A scramjet's special design allows it to obtain oxygen from the air that flows through the engine. And it does so without letting the fast-moving air put out the combustion flames. However, a scramjet engine works properly only at speeds greater than five times the speed of sound. A booster rocket carried the Hyper-X to an altitude of about 100,000 feet for its test flight. The aircraft's record-beating flight lasted just 11 seconds. Although the little plane's self-powered flight lasted only 11 seconds, that brief journey on March 27 makes a major milestone on the way to a new breed of very fast airplanes, comments Werner J. A. Dahm of the University of Michigan in Ann Arbor. In the future, engineers predict, airplanes equipped with scramjet engines could transport cargo quickly and cheaply to the brink of space. Such hypersonic jets could potentially carry passengers anywhere in the world in just a few hours.
Out of the three experimental Hyper-X aircrafts built for NASA, only one is now left. The agency has plans for another 11-second hypersonic flight, this time at 10 times the speed of the sound.

单选题 The Hyper-X broke the record because______.
【正确答案】 D
【答案解析】[解析] Hyper-X之所以打破纪录是因为它的飞行速度是音速的7倍。它不是第一架空气喷气式飞机，而是从7倍音速的超音速飞行，所以A和C都不对。Hyper-X的试飞并未绕赤道飞行，所以B也是错误选项。
单选题 What kind of an engine did the Hyper-X use?
【正确答案】 B
【答案解析】[解析] 第四段讲了三种发动机的氧气来源：喷气式发动机是从空气中汲取氧气，火箭发动机必须自携氧气，而超音速冲压喷气发动机则不必自携氧气，而这正是Hyper-X使用的发动机装置。
单选题 What is NOT true about the scramjet engine?
【正确答案】 A
【答案解析】[解析] 根据第四段内容，B、C、D都是正确的说法。第四段第四句告诉我们：超音速冲压喷气发动机和火箭发动机速度相同，故A说法不正确。
单选题 What did Werner J.
【正确答案】 D
【答案解析】[解析] 文章的第四段中，密歇根大学的研究人员Werner J. A. Dahm说，Hyper-X的试飞成功只是研制一种新式快速飞机过程中的一个里程碑(a major milestone on the way to a new breed of very fast airplanes)，而不是新型飞机的诞生。所以，D是正确选择，A是错误选择。B也不是Werner J.A.Dahm想要表达的意思。C是其他工程师而不是Werner J.A.Dahm说的话。
单选题 What has NASA planned to do?
【正确答案】 A
【答案解析】[解析] 答案可在最后一段找到。