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  3. 63. The investigation of the accident lasted for almost two years. Sand: as

63. The investigation of the accident lasted for almost two years. Sand: as

游客2024-08-19  61
问题 63. The investigation of the accident lasted for almost two years.
    Sand: as children we play on it and as adults we relax on it. It is something we complain about when it gets in our eye on a windy beach, and praise when it is made into sand castles.
    But we don’t often look at it. If we did, we would discover an account of a geological past and a history of sea life that goes back thousands and, in some cases, millions of years.
    Sand covers not just seashores, but also ocean beds, deserts and mountains.
    64.______
    And it is a major element in manufactured products too—concrete is largely sand, while glass is made of little else.
    65______
    Well, it is larger than fine dust and smaller than shingle. In fact, according to the most generally accepted scheme of measurement, grains can be called sand if their diameter is greater than 0. 06 of a millimetre and less than 0. 6 of a millimetre.
    Depending on its age and origin, a particular sand can consist of tiny stones or porous grains through which water can pass.
    66 ______
    They have come from the breaking down of rocks, or from the dead bodies of sea creatures, which collect on the bottom of the oceans, or even from volcanic eruptions.
    67 ______
    If it is a dazzling white, its grains may come from nearby coral, from crystalline quartz rocks or from gypsum, like the white sand of New Mexico. On Pacific Islands, jet black sands form from volcanic minerals. Other black beaches are magnetic and are mined for iron ore.
    68______
    It washes rock into streams and rivers and down to the sea, leaving behind softer materials. By the time it reaches the sea, the hardest rocks remain but everything else has been broken into tiny particles of 0. 02 millimetre diameter or less. The largest pieces fall to the bottom quickly, while smaller particles float and settle only slowly in deeper water, which is why the sandy beach on the shoreline so often turns to mud further out.
    69______
    If the individual fragments still have sharp edges, you can be sure they were formed fairly recently. This is the case on the island of Kamoama in Hawaii, where a beach was created after a volcanic eruption in 1990. Molten lava spilled into the sea and exploded into glassy droplets.
    It seems that when the poet William Blake saw infinity in a grain of sand he was not far wrong.   
    70____
    Sand is an irreplaceable industrial ingredient which has many uses.
    Sand cushions our land from the force of the sea, and geologist say it often does a better job protecting our shores than the most advanced coastal technology.
A. These may have the shape of stars or spirals, their edges rough or smooth.
B. It is one of the most common substances on earth.
C. In addition, it has one vital function which you might never even notice.
D. Rain is all important force in the creation of beaches.
E. In the great slow cycle of the earth, sand that was once rock can turn to rock again.
F. What exactly is sand?
G. Colour is another clue to the origins of sand.
H. It can be difficult to date the sand on a beach accurately but it is possible to get a general idea of whether or not the sand is "young”or "old". [br]
选项
答案 B
解析 空格前面一句话说沙子不仅覆盖了海滩，而且还覆盖了大洋的底部、沙漠和高山，根据逻辑推测，那么沙子在地球上就是一种常见的物质。
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