It can be known from the passage that increase in the salinity of ocean water is caused by______.

A．give an example of cold water salinity
B．point out the location of deep waters
C．compare Antarctic waters with Arctic waters
D．indicate that this body of .water has salinity variations

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.