英语四级仔细阅读练习题

　　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.