练习：
1． The Hyper-X broke the record because
A it was the first air-breathing jet plane．
B it flew along the equator．
C it flew at speeds smaller than five times the speed of sound．
D it traveled at a supersonic speed．
2． What kind of an engine did the Hyper-X use?
A A jet engine that gets oxygen from the air．
B A scramjet engine that doesn’t carry its own oxygen supply．
C A rocket engine that carries its own supply of oxygen．
D A iet engine that uses no oxygen．
3． What is NOT true about the scramjet engine?
A It goes slower than a rocket．
B It extracts oxygen from the air that flows through the engine．
C It works only at speeds greater than five times the speed of sound．
D It doesn’t carry its own oxygen supply．
4． What did Werner J．A．Dahm of the University of Michigan say about the Hyper-X test flight?
A It indicated the birth of a very fast airplane．
B It was self-powered，so it lasted only 11 seconds．
C It can transportcargo quickly and cheaply to the brink of space．
D It is a major milestone in the journey of making a new type of very fast airplanes,
5． What has NASA planned to do?
A To make another 11-second hypersonic flight at 10 times the speed of the sound．
B To make three more Hyper-X experiments．
C To retest the aircraft that is left．
D To make the aircraft fly higher and longer．
答案与题解：
1． C 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，也不是第一架超音速飞机，所以A和D都不对。Hyper-X的试飞并未绕赤道飞行，所以B也是错误的选择。
2． B 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白携氧气，而这正是Hyper-X使用的发动机装置。
3． A 根据第五段内容，B、C、D都是正确的说法。第四段最后一句告诉我们，A的说法是不正确的。
4． D 文章的第六段中，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是其他下程师而不是Werner J．A．Dahm说的话。
5． A 答案可在最后一段找到。
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