[单项选择]The two main requirements of aircraft design are______.
A. speed and cost
B. reliability and passenger comfort
C. lightness and dependability
D. ability to stay up in the air and reliability

[单项选择]There are two main requirements before the fifth-generation computer can become a reality and it is these that scientists are _________.
A. anticipating
B. tackling
C. manipulating
D. speculating

[单项选择]Western scholars generally recognize two main kinds of riddle: the descriptive riddle and the witty question.
A. shrewd
B. absurd
C. controversial
D. exhilarating

[单项选择]What is the main idea of paragraph two

[单项选择]What is the main idea of last two paragraphs
A. The difference and resemblance of using language between human beings and animals.
B. The function of language.
C. How the human beings produce the sound.
D. Humans are characterized in many ways to use symbolic communication.

[单项选择]What is the main difference between the two parts of the city
A. The colour of the buildings
B. The age of the buildings
C. The colour of the roofs
D. The length of the streets

[单项选择]

Two main techniques have been used for training elephants, which we may call respectively the tough and the gentle. The former method simply consists of setting an elephant to work and beating him until he does what is expected of him. Apart from any moral considerations this is a stupid method of training, for it produces a resentful animal who at later stage may well turn into a man-killer. The gentle method requires more patience in the early stages, but produces a cheerful, good-tempered elephant who will give many years of loyal service.
The first essential in elephant training is it assigns to the animal a single mahout who will be entirely responsible for the job. Elephants like to have one master just as dogs do; and are capable of a considerable degree of personal auction. There are even stories of half trained elephant calves who have refused to feed and pained to death when by some unavoidable circum stance they have been deprived of their own trainer. Such ext
A. two techniques used for training elephants
B. the inhumane method used in training elephants
C. how to train the elephant
D. the bad relationship between human beings and elephants

[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