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  3. When we analyze the salt salinity(盐浓度)of ocean waters, we find that it varies only slightly from place to place. Nevertheless, s

When we analyze the salt salinity(盐浓度)of ocean waters, we find that it varies only slightly from place to place. Nevertheless, s

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问题     When we analyze the salt salinity(盐浓度)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 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.
Which of the following statements is TRUE according to the passage?
选项 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.
答案D
解析 按照出题顺序，此题考查的是海水盐度变化的第三个原因。根据第四段可知，海水冻冰后．杂质析出，因此冰下的海水比冰的盐度高；冰融化后，海水盐度又会降低。所以答案为D，即海水温度与盐度有很大关系。
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