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1、1995年托福阅读真题Questions 1-13Atmospheric pressure can support a column of water up to 10 meters high. But plants can move wat er much higher, the sequoia tree can pump water to its very top, more than 100 meters above the ground. Until the end of the nineteenth century, the movement of water in trees an
2、d other tall plants was a mystery. Some botanists hypothesized that the living cells of plants acted as pumps, But many experiments demonstrated hat the stems of plants in which all the cells are killed can still move water to appreciable heights. Other explanations for the movement of water in plan
3、ts have been based on root pressur e, a push on the water from the roots at the bottom of the plant. But root pressure is not nearly great enough to push water to the tops of tall trees. Furthermore, the conifers, which are among the tallest trees, have unusually low root pressures.If water is not p
4、umped to the top of a tall tree, and if it is not pushed to the top of a tall tree, then we may ask, How does it get there? According to the currently accepted cohesion-tension theory, water is pulled there. The pull on a rising column of water in a plant results from the evaporation of water at the
5、 top of the plant. As water is lost from the surface of the leaves, a negative pressure, or tension, is created. The evaporated water is replaced by water moving from inside the plant in unbroken columns that extend from the top of a plant to its roots. The same forces that create surface tension in
6、 any sample of water are responsible for the maintenance of these unbroken columns of water. When water is confined in tubes of very small bore, the forces of cohesion (the attraction between water molecules) are so great that the strength of a column of water compares with the strength of a steel w
7、ire of the same diameter. This cohesive strength permits columns of water to be pulled to great heights without being broken.1. How many theories does the author mention? (A) One(B) Two (C) Three (D) Four2. The passage answers which of the following questions? (A) What is the effect of atmospheric p
8、ressure on foliage? (B) When do dead cells harm plant growth?(C) How does water get to the tops of trees?(D) Why is root pressure weak3. The word demonstrated in line5 is closest in meaning to(A) ignored (B) showed (C) disguised(D) distinguished4. What do the experiments mentioned in lines 4-6 prove
9、? (A) Plant stems die when deprived of water(B) Cells in plant stems do not pump water(C) Plants cannot move water to high altitudes(D) Plant cells regulate pressure within stems5. How do botanists know that root pressure is not the only force that moves w ater in plants? (A) Some very tall trees ha
10、ve weak root pressure.(B) Root pressures decrease in winter. (C) Plants can live after their roots die.(D) Water in a plants roots is not connected to water in its stem.6. Which of the following statements does the passage support? (A) Water is pushed to the tops of trees.(B) Botanists have proven t
11、hat living cells act as pumps.(C) Atmospheric pressure draws water to the tops of tall trees.(D) Botanists have changed their theories of how water moves in plants.7. The word it in line 11 refers to(A) top (B) tree (C) water(D) cohesion-tension theory.8. The word there in line 10 refers to(A) treet
12、ops(B) roots(C) water columns(D) tubes9. What causes the tension that draws water up a plant? (A) Humidity(B) Plant growth(C) Root pressure(D) Evaporation10. The word extend in line 13 is closest in meaning to(A) stretch (B) branch (C) increase (D) rotate11. According to the passage, why does water
13、travel through plants in unbroken columns? (A) Root pressure moves the water very rapidly.(B) The attraction between water molecules in strong.(C) The living cells of plants push the water molecules together. (D) Atmospheric pressure supports the columns.12. Why does the author mention steel wire in
14、 line 17? (A) To illustrate another means of pulling water(B) To demonstrate why wood is a good building material(C) To indicate the size of a column of water(D) To emphasize the strength of cohesive forces in water13. Where in the passage does the author give an example of a plant with low root pre
15、ssure? (A) Lines 2-3(B) Lines 3-5 (C) Lines 6-7 (D)Lines8Question 14-22Mass transportation revised the social and economic fabric of the American city in three fundamental ways. It catalyzed physical expansion, it sorted out people and land uses, and it accelerated the inherent instability of urban
16、life. By opening vast areas of unoccupied land for residential expansion, the omnibuses, horse railways, commuter trains, and electric trolleys pulled settled regions outward two to four times more distant from city centers than they were in the pre-modern era. In 1850, for example, the borders of Boston lay scarcely two miles from the old busi
