这次的题目比较多~~~有一篇阅读题还有两句难句的翻译~
大家不着急哈，有时间的时候再来作题~很久以后才发奖励= = *
阅读题+80HY，翻译题加50HY~一定要隐藏答案哦~   

科普：自然世界 348词    建议作题时间：8分钟 

If the salinity of ocean waters, that is, how much salt the ocean waters contain, is analyzed, ti si found to vary only slightly from place to place. Neverthelee, 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 — change of liquid water to water vapor. In this manner, the salinity is increased, since the salts stay behind. If this is carried to the extreme, of course, white crystals of salt would be left behind; this 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 the rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the additon of fresh water by precipitation or runoff.

Normally, in tropical 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 the 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, off Antarctica, the densest water in the oceans 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 portions of the oceans of the world.

1. There is no _________ of the salinity between different places in the sea.

2. Precipitation makes the salinity of an ocean decrease becouse it __________.

3. Where is the process of evaporation strongest?

4. What happens to the salt in the seawater when it is frozen?

5. The densest water formed in the Weddell Sea is an example of _________.