[单项选择]

Passage Two
Among the question of design, construction, and operation remaining to be solved before commercial airliners travel faster than sound is the difficult problem of sonic boom (声震) , the explosive sound generated when an object moves through the air at supersonic speed(超音速).
A sound is a pressure disturbance: a sonic boom, like other explosive sounds, is the result of an abrupt change in pressure. An airplane in subsonic flight produces weak changed in pressure, but because these disturbances travel at the speed of sound, they move faster than the airplane and stay in front of it. In effect, these disturbances warn the air to get out of the way, and the an does just jet, however, gets ahead of its own pressure disturbances. Consequently a wave of suddenly com pressed air--a shock wave--builds up and is thrown off like the wave ;hat spreads from the bow of a speedboat.
Can sonic booms be eliminated The answer is a categorical negative--they
A. explosive
B. caused by compressed tar
C. a pressure disturbance
D. shock wave

[单项选择]

Passage Two
Among the question of design, construction, and operation remaining to be solved before commercial airliners travel faster than sound is the difficult problem of sonic boom (声震) , the explosive sound generated when an object moves through the air at supersonic speed(超音速).
A sound is a pressure disturbance: a sonic boom, like other explosive sounds, is the result of an abrupt change in pressure. An airplane in subsonic flight produces weak changed in pressure, but because these disturbances travel at the speed of sound, they move faster than the airplane and stay in front of it. In effect, these disturbances warn the air to get out of the way, and the an does just jet, however, gets ahead of its own pressure disturbances. Consequently a wave of suddenly com pressed air--a shock wave--builds up and is thrown off like the wave ;hat spreads from the bow of a speedboat.
Can sonic booms be eliminated The answer is a categorical negative--they
A. discover what causes the sonic boom
B. find a means of eliminating the sonic boom
C. produce the sonic boom at low altitudes
D. reduce the sonic boom to tolerable levels

[单项选择]Weighing among two to five kilograms in adults, the skin is the largest organ of the human body.

[单项选择]The question which is discussed in the passage is
A. how historians should explain the origins of the conditions in the Chicago meat-packing industry,
B. why it is difficult to determine the actual nature of the conditions in the Chicago meat- packing industry.
C. why a particular account of the conditions in the Chicago meat-packing industry is inaccurate.
D. what should be included in any account of the Chicago meat-packers’ role in the national labor movement.

[单项选择]

Passage One
If the teacher asks a question, you are expected to give an answer. If you do not understand the question, you should raise your hand and ask the teacher to repeat the question. If you do not know the answer, it is all right to tell the teacher that you do not know. Then he or she knows what you need to learn.
There is no excuse for not doing your homework. If you are absent, you should call your teacher or someone who is in your class and ask for the assignment. It is your responsibility to find out what assignments you have missed. It is not the teacher’s responsibility to remind you of missed assignments.
You must not be absent on a test day. If you are seriously ill, call and let the teacher know you will not be there for the test. If your teacher allows make-up tests, you should take the test within one or two days after returning to class. Serious illness is the only reason for missing a test.
Be on time! It is consid
A. Principles of the Classroom.
B. Rules for Students.
C. American Classroom Customs.
D. International Customs.