2019英語四級《仔細(xì)閱讀》練習(xí)題(10)

1、2019 英語四級仔細(xì)閱讀練習(xí)題 (10)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 w

2、ater 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

3、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 b

4、y 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 th

5、e 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 h

6、as 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

7、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 watersB. the causes of the variation in oceanic salinityC. the importance of the changes in oceanic salinityD. the different forms of salts

8、in ocean waters27.It can be known from the passage that increase in the salinity of ocean water is causedby.A. melting of sea ice B. precipitationC. evaporation D. supplement of salt28. Which of the following is not the cause of the decrease in the oceanic salinity?A. Precipitation. B. Rain and snow

9、.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 isA. to give an example of cold-water salinityB. to point out the location of deep watersC. to make a comparison between hot-wa