Question

2．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 （減少） of water from the ocean by means of evaporation （蒸發(fā)）．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．
60．This passage mainly tells us aboutB．
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
61．It can be known from the passage that increase in the salinity of ocean water is caused byC．
A．melting of sea ice                  
B．precipitation   
C．evaporation                     
D．supplement of salt
62．Which of the following is not the cause of the decrease in the oceanic salinity？C
A．Precipitation．
B．Rain and snow．
C．Formation of ice．
D．Addition of water by rivers．

Answer 1

分析 本文是一篇科教類閱讀，屬于說明文，當(dāng)我們分析海水的鹽度（鹽度）時，我們發(fā)現(xiàn)它們在不同地點之間變化很�。�然而，其中一些小的變化是重要的．本文以此展開講述，主要講述了導(dǎo)致海洋鹽度變化的三個基本過程．

解答 60．B．主旨大意題．閱讀全文，根據(jù)文章內(nèi)容可知，本文主要講述了導(dǎo)致海洋鹽度變化的三個基本過程．故選B，
61．C．細(xì)節(jié)理解題．根據(jù)One of these is the subtraction （減少） of water from the ocean by means of evaporation （蒸發(fā)）．In this manner，the salinity is increased，since the salt stays behind．可知，蒸發(fā)使海水中的鹽分增加．故選C．
62．C．細(xì)節(jié)理解題．根據(jù)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．可知，冰的形成增加了海水的鹽度．故選C．

點評 本文是一篇科教類閱讀，題目涉及多道細(xì)節(jié)理解題，主旨大意題．做題時學(xué)生應(yīng)仔細(xì)閱讀原文，把握文章主要內(nèi)容，聯(lián)系文章上下文內(nèi)容并結(jié)合所給選項含義，從中選出正確答案，一定要做到有理有據(jù)，切忌胡亂猜測