JOE’S BEEN WALKING WITH A SPRING IN HIS STEP EVER SINCE HE FOUND OUT...

Câu 30

: Joe’s been walking with

a spring in his step

ever since he found out he was

getting a promotion.

A. a bad and sorrow mood

B. a joyful and energetic mood

C. a happy and excited mood

D. a worried and depressed moon

Read the following passage and mark the letter A, B, C or D on your answer

sheet to indicate the correct answer to each of the questions that follow from

31 to 38.

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 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 salt behind. If

this

is carried to the extreme, of course, white crystals of

salt would be left behind.

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 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 portions of the oceans of the world.