2022年12月大学英语六级考试模拟题及答案(五)

　　27. The word “this” in the sentence “This is logical” most probably refers to.

　　A. that our ancestors knew plants are the basis of the food pyramid for all living things

　　B. that our ancestors' knowledge about plants and their properties was very detailed and organized

　　C. that extensive knowledge about plants and their properties are essential in the cultivation of crops in pre—industrial societies

　　D. that a detailed learning of plants and their properties was not obtained until the pre—industrial societies came into being

　　28. According to the author, when did our knowledge of botany become less distinct?

　　A. As our society become industrialized.

　　B. As our direct contact with plants increases.

　　C. As urbanization took place.

　　D. As we became less interested in the extensive botanical knowledge.

　　29. Why does the author mention tribes living in the jungle of the Amazon in the passage?

　　A. To show that people who have no contact with modern civilization have no idea what the term botany means.

　　B. To show even the most primitive people have extensive knowledge about plants and their properties.

　　C. To show how important the study of botany is to human beings.

　　D. To show that how people unconsciously come into possession of an amazing amount of botanical knowledge.

　　30. The relationship between botany and agriculture is similar to the relationship between the study of animals and .

　　A. sheep raising B. bird watching

　　C. deer hunting D. horse riding

　　Questions 31 to 35 are based on the following passage:

　　The great advance in rocket theory 40 years ago showed that liquid—fuel rocket 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 solid—fuel rockets with solid fuels about as powerful as liquid—fuels have made their appearance, and it is a favorite layperson's 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 re—ignited when desired. In addition, the thrust can be made to vary by adjusting the speed of the fuel pumps. A solid—fuel 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 solid—fuel rocket, it is ready for action at very short notice. A liquid—fuel rocket has to be fueled first and cannot be held in readiness for very long after it has been fueled. However, once a solid—fuel rocket has been ignited, it will keep burning. It cannot be stopped and re—ignited whenever desired (it could conceivably be stopped and re—ignited after a pre—calculated time of burning has elapsed) and its thrust cannot be varied. Because a solid—fuel rocket can be kept ready for a long time, most military missiles employ solid fuels, but human—piloted space flight needs the fine adjustments that can only be provided by liquid fuels. It may be added that a liquid—fuel rocket is an expensive device; a large solid—fuel 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. Which of the following is implied in the passage?

　　A. Rockets using liquid fuel was not available 40 years ago although researches were being done on the practicability of using liquid fuel in rockets.

　　B. It was not until the last decade that rockets using solid fuels made their appearance.

　　C. Complicated rockets using solid fuel have the advantage of flexibility and adjustability that liquid—fuel rockets don't possess.

　　D. Liquid fuel costs about 10 times as much as the solid fuel costs.