Liquid water changes to vapor, ___ is called evaporation.

A.solid

B.vapour

C.liquid

D.air

A．water vapor

B．the temperature of the air

C．humid air

D．water vapor changes to liquid water when the air is cold enough

If the salinity(含盐量) of ocean waters is analyzed, it is round 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 of water from the ocean by means of evaporation—conversion of liquid water to water vapor. In this manner, the salinity is increased, since the sales stay behind. If this is carried to the extreme, of course, white crystals of 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 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 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, 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.

What does the passage mainly discuss？

A．The elements of salt.

B．The bodies of water of the world.

C．The many forms of ocean life.

D．The salinity of ocean water.

A.water,river,liquid都不会出现

B.water,river,liquid必须同时出现

C.water,river,liquid出现一个即可

D.water,river,liquid必须出现两个

The cooling liquid used for the cylinder may be referred to as _____.

A.jacket water

B.make-up water

C.boiler water

D.flushing water

A.liquid

B.vapor

C.water drop

D.drip

A hygroscopic cargo is defined as a cargo ______．

A.capable of absorbing moisture in the form of a gas

B.capable of giving off moisture in the form of a liquid

C.that is shipped in a liquid state

D.that will ignite in contact with water

A.The CHANEL whitening lotion prevents the skin from water shortage.

B.The CHANEL whitening liquid prevents the skin from water shortage.

C.The CHANEL whitening juice prevents the skin from water shortage.

D.The CHANEL whitening milk prevents the skin from water shortage.

cular pressure immediately changes into steam after admitted to a chamber at a lower pressure is called _____.

A.boiling off

B.flash evaporation

C.condensation

D.none of the above