题目

Mysteries of the sea
The sea is the largest unknown part of our world.it covers 71 percent of the earth.there is still much to be discovered about this
vast blanket of water.
Some scientists are studying ways of bringing the ocean's huge supply of water to the deserts of the word
Others hope to control the weather by learning more about the exchange of heat and moisture between the ocean and the air.Still others are studying the ways in which sound travels and is affected by water and heat.What happens when sea water touches different elements is another subject of study.There are just a few of the questions to which oceanographers are devoting their energies
One of the most ineresting projects in oceanography is the work of mapping the ocean floor.Only a very small part os it has been mapped .This was not important when only surface ships sailed the world's oceans,but it can mean the difference between life and death to men in submarines
Long ago there was only one way to find out how deep the ocean was.
A sea-man could throw a weighted rope over the side of his ship.Then he pulled the rope up after it had reached the bottom.
but this was not a very exact way of measuring.
In the twentieth century a better way was found.sound was used to measure the ocean .An American Navy ship sailed into a narrow strip of water to conduct an experiment.seamen dropped a number of devices that would burst with a loud noise when they hit the bottom.And a little instrument that had been invented measured the time it took for the sound to reach the ship.This has helped oceanographers map the ocean floor.
Underwater photograph is also important in mapping parts of the ocean floor.with the new methods that have been perfected,cameras can take pictures of the underwater valleys,even in color.
If the waters of the ocean could be moved away,the sea floor with its wide valleys,uneven mountains and submarine rivers would be an unbelievable sight.Around the edges of the continents the ocean floor is flat and the water does not become much deeper for about thirty miles.Where there are high young mountains along the coast,this flat part may be much less than 30 miles.But where rivers flow into the sea,the flat area nay extend foe hundreds of miles.
The region near the continents,where the water is not so deep,is the place where the ocean's greatest riches in marine life are found.Below these living creatures and plants are the largest known quantitise of minerals.
At the end of the flat part the sea floor suddenly drops down,forming deep hollows which are shaped like bowls.these huge hollows hold most of the world's water
Imagine,if you can,a mountain chain stretching 40,000 miles around the earth.it is hard to believe that this great underwater chain of mountains encircling the earth was discovered only a few years ago.
（英译汉）：我的分不多，因为只有这么多，

提问时间：2021-02-08

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