阅读理解

　　If the salinity of ocean waters is analyzed it is found to vary 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(减少)of water from the ocean by means of evaporation(蒸发)conversion of liquid water to water vapor. In this manner the salinity is increased since the salts stay behind.

　　The opposite of evaporation is precipitation(降水) such as rain by which water is added to the ocean. This may occur in areas of high rainfall or in coastal regions where rivers flow into the ocean.

　　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 rivers dilute(稀释)the sea salinity is somewhat lower than in other oceanic area.

　　A third process by which salinity may be altered is associated (关联)with the formation and melting of sea ice. When seawater is frozen the dissolved(溶解的)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 Weddle Sea off America 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)All of the following are processes that decrease salinity except ________.

[　　]

A．precipitation　　　　B．evaporation

C．rivers dilute　　　　D．sea ice melts

(2)The salinity of the oceanic water is generally higher in ________.

[　　]

A．tropical areas　　　　B．coastal region

C．turbulent areas　　　　D．rainy regions

(3)Which of the following statements is NOT TRUE according to the passage?

[　　]

A．Various factors combine to cause variations in the salinity of water.

B．As a result of the formation of ocean ice water salinity decreases.

C．The salinity of the water near the bottom of the oceans is relatively high.

D．In coastal areas the ocean is diluted by rivers.

(4)The major points discussed in the passage is ________.

[　　]

A．the subtraction of water

B．the conversion of liquid water to water vapor

C．the salinity of ocean water

D．the effect of precipitation on the salinity of ocean water