24. Problems that might impede effective communication are caused by________.
A. the nature of symbol
B. the semantic variation in their meanings
C. nonverbal messages
D. all of the above
25. Which of the following is critical to effective communication?
A. Creating a message.
B. Developing empathy for the receiver.
C. Overcoming noise through effective feedback.
D. Choosing the most appropriate channel or channels of media.
Passage Two
Questions 26 to 30 are based on the following passage.
Scientists claim that air pollution causes a decline in the world's average air temperature. In order to prove that theory, ecologists have turned to historical data in relation to especially huge volcanic eruptions. They suspect that volcanoes affect weather change that are similar to air polluiton.
One source of information is the effect of the eruption of Tambora, a volcano in Sumbawa, the Dutch East Indias, in April 1815. The largest recorded volcanic eruption, Tambora threw 150 million tons of fine ash into the stratosphere(平流层). The ash from a volcano spreads worldwide in a few days and remains in the air for years. Its effect is to turn incoming solar radiation into space and thus cool the earth. For example, records of weather in England show that between April and November 1815, the average temperature had fallen 4.5 . During the next twentyfour months, England suffered one of the coldest periods of its history. Farmers' records from April 1815 to December 1818 indicate frost throughout the spring and summer and sharp decreases in crop and livestock markets. Since there was a time lag(滞后) of several years between cause and effect, by the time the world agricultural commodity community had deteriorated, no one realized the cause.
Ecologists today warn that we face a twofold menace. The everpresent possibility of volcanic eruptions, such as that of Mr. St. Helens in Washington, added to man's pollution of the atmosphere with oil, gas, coal, and other polluting substances, may bring us increasingly colder weather.
26. It is believed that the earth gets colder when ________.
A. volcanoes erupt
B. the air is polluted by modern man
C. the rays of the sun are turned into space
D. all of the above
27. The effects of Tambora's eruption were ________.
A. felt mainly in the Dutch East Indias
B. of several day's duration worldwide
C. evidence of pollution's cooling the earth
D. immediately evident to the world's scientists
28. The cause of cold weather in England from 1815 to 1818 was ________.
A. decreased crop and livestock production
B. volcanic ash in the atmosphere
C. pollution caused by the Industrial Revolution
D. its proximity to the North sea
29. No one realized the cause of the deterioration of the world agricultural commodity market because ________.
A. there was a long delay between cause and effect
B. the weather is beyond our comprehension
C. weather forecasts were inaccurate
D. ecologists didn't exist until modern times
30. If, as some scientists predict, the world ends in ice, what might be the cause?
A. Modern man's pollution of the air.
B. Volcanic eruptions.
C. Obliteration(破坏) of solar radiation.
D. All of the above.
Passage Three
Questions 31 to 35 are based on the following passage.
The great advance in rocket theory 40 years ago showed that liquidfuel rockets were far superior in every respect to the skyrocket with its weak solid fuel, the only kind of rocket then known. However, during the last decade, large solidfuel rockets with solid fuels about as powerful as liquid fuels have made their appearance, and it is a favorite layman's(外行) question to inquire which one is “better.” The question is meaningless; one might as well ask whether a gasoline or a diesel engine is “better.” It all depends on the purpose. A liquid fuel rocket is complicated, but has the advantage that it can be controlled beautifully. The burning of the rocket engine can be stopped completely; it can be reignited(重新点火) when desired. In addition, the thrust can be made to vary by adjusting the speed of the fuel pumps. A solidfuel rocket, on the other hand, is rather simple in construction, though hard to build when a really large size is desired. But once you have a solidfuel rocket, it is ready for action at very short notice. A liquidfuel rocket has to be fueled first and cannot be held in readiness for very long after it has been fueled. However, once a solidfuel rocket has been ignited, it will keep buming. It cannot be stopped and reignited whenever desired (it could conceivably be stopped and reignited after a pre calculated time of burning has elapsed) and its thrust cannot be varied. Because a solidfuel rocket can be kept ready for a long time, most military missiles employ solid fuels, but manned spaceflight needs the fine adjustments that can only be provided by liquid fuels. It may be added that a liquidfuel rocket is an expensive device; a large solidfuel rocket is, by comparison, cheap. But the solid fuel, pound per pound, costs about 10 times as much as the liquid fuel. So you have, on the one hand, an expensive rocket with a cheap fuel and on the other hand a comparatively cheap rocket with an expensive fuel.
31. The author feels that a comparison of liquidand solidfuel rockets shows that ________.
A. neither type is very economical
B. the liquidfuel rocket is best
C. each type has certain advantages
D. the solidfuel rocket is best
32. The most important consideration for manned space flight is that the rocket be ________.
A. inexpensive to construct
B. capable of lifting heavy spacecraft into orbit
C. easily controlled
D. inexpensive to operate
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