四級英語閱讀強化習題及答案

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　　四級英語閱讀強化習題***一***

　　When we analyze the salt salinity***鹽濃度*** of ocean waters, we find that it varies only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation. In this manner, the salinity is increased, since the salt stays behind. If this is carried to the extreme, of course, white salt would be left behind; this, by the way, is how much of the table salt we use is actually obtained.

　　The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted ***稀釋*** so that the salinity is decreased. This may occur in areas of high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation.

　　Normally, in hot regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.

　　A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind.. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.

　　In the Weddell Sea, the densest water in the ocean is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portion of the oceans of the world.

　　26. This passage mainly tells us about_______.

　　A. the analysis of the salinity of ocean waters

　　B. the causes of the variation in oceanic salinity

　　C. the importance of the changes in oceanic salinity

　　D. the different forms of salts in ocean waters

　　27.It can be known from the passage that increase in the salinity of ocean water is caused

　　by______.

　　A. melting of sea ice B. precipitation

　　C. evaporation D. supplement of salt

　　28.Which of the following is not the cause of the decrease in the oceanic salinity?

　　A. Precipitation. B. Rain and snow.

　　C. Formation of ice. D. Addition of water by rivers.

　　29.Which of the following statements is TRUE according to the passage?

　　A. Oceanic salinity has great effect on sea life.

　　B. Many factors combine to cause changes in oceanic salinity.

　　C. The movement of the water is related to the amount of salt.

　　D. The temperature of the water has much to do with the oceanic salinity.

　　30.The purpose of mentioning the Weddell Sea is_______.

　　A. to give an example of cold-water salinity

　　B. to point out the location of deep waters

　　C. to make a comparison between hot-water salinity and cold-water salinity

　　D. to show that the water in the Weddell Sea varies in salinity from place to place

　　四級英語閱讀強化習題答案

　　26. B 27. C 28. C 29. D 30. A

　　四級英語閱讀強化習題***二***

　　There is evidence that the usual variety of high blood pressure is, in part, a familial disease. Since families have similar genes as well as similar environments, familial diseases could be due to shared genetic influences, to shared environmental factors, or to both. For some years, the role of one

　　environment factor commonly shared by families, namely dietary salt ***i.e., sodium chloride***, has been studied at Brookhaven National Laboratory. These studies suggest that long excess salt intake can lead to high blood pressure in man and animals. Some individuals, however, and some rats consume large amounts of salt without developing high blood pressure. No matter how strictly all environmental factors were controlled in these experiments, some salt-fed animals never developed hypertension whereas a few rapidly developed very severe hypertension followed by early death. These marked variations were interpreted to result from differences in genetic constitution.

　　By mating long successive generations of those animals that failed to develop hypertension from salt intake, a resistant strain ***the " R" strain*** has been evolved in which consumption of large quantities of salt fails to influence the blood pressure significantly. In contrast, by mating only animals that quickly develop hypertension from salt, sensitive strain ***the "S" strain*** has also been developed.

　　The availability of these two strains permits investigations possible. They provide a plausible laboratory model on which to investigate some clinical aspects of the human hypertension. More important, there might be the possibility of developing methods by which genetic susceptibility ***敏感性*** of human beings to high blood pressure can be defined without waiting for its appearance. Radioactive sodium 22 was an important "tool" in working out the characteristics of the sodium chloride metabolism.

　　21. The study of the effects of salt on high blood pressure was carried out_______.

　　A. as members of the same family tend to use similar amounts of salt

　　B. to explore the long-term use of a sodium based substance

　　C. because it was proven that salt caused high blood pressure

　　D. because of the availability of chemically pure salt and its derivatives

　　22. The main difference between "S" and "R" rats is their_______.

　　A. need for sodium 22 B. rate of mating

　　C. reaction to salt D. type of blood

　　23. We can infer from the article that sodium 22 can be used to_______.

　　A. control high blood pressure

　　B. cure high blood pressure caused by salt

　　C. tell the "S" rats from the "R" rats

　　D. determine what a sodium chloride metabolism is like

　　24. The most beneficial results of the research might be_______.

　　A. development of diets free of salt

　　B. an early cure for high blood pressure

　　C. control of genetic agents that cause high blood pressure

　　D. the early identification of potential high blood pressure victims

　　25. Which of the statements best relates the main idea of this article?

　　A. When salt is added rats and human beings react similarly.

　　B. The near future will see a cure for high blood pressure.

　　C. The medical field is desperately in need of research.

　　D. A tendency toward high blood pressure may be a hereditary factor.

　　四級英語閱讀強化習題答案

　　21. A 22. C 23. D 24. D 25. D