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.
标准答案： C，B，A，D，A