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  3. When aluminum was first produced about a hundred and fifty years ago, it was so difficult to separate from the ores(矿石) in which

When aluminum was first produced about a hundred and fifty years ago, it was so difficult to separate from the ores(矿石) in which

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问题     When aluminum was first produced about a hundred and fifty years ago, it was so difficult to separate from the ores(矿石) in which it was found that its price was higher than that of gold. The price remained high until a new process was discovered for refining the metal with the aid of electricity approximately three quarters of a century later. The new method was so much cheaper that aluminum became practical for many purposes, one of which was making pots and pans.
    Aluminum is lightweight, rustproof and easily shaped into different forms. By mixing it with other metals, scientist have been able to produce a variety of alloys, some of which have the strength of steel but weigh only one third as much.
    Today, the uses of aluminum are innumerable. Perhaps its most important use is in transportation. Aluminum is found in the engines of automobiles, in the hulls of boats. It is also used in many parts of airplanes. In fact, the huge "airbus" planes would probably never have been produced if aluminum did not exist. By making vehicles lighter in weight aluminum has greatly reduced the amount of fuel needed to move them. Aluminum is also being used extensively in the building industry in some countries.
    Since aluminum is such a versatile(多用的) metal, it is fortunate that bauxite(铝土矿) , which is one of its chief sources, is also one of the earth’s most plentiful substances. As the source of aluminum is almost inexhaustible, we can expect that more and more uses will be found for this versatile metal.
Aluminum is______.
选项 A、lightweight, rustproof but not easily shaped into different forms
B、heavyweight, rustproof and easily shaped into different forms
C、lightweight, rustproof and easily shaped into different forms
D、lightweight and easily shaped into different forms but it is easy to become rusty
答案C
解析 根据文章第二段第一句中的(铝的重量轻、防生锈、易成形)所以选择C。A项 的意思不全，只说了其两个特征：重量轻，不易生锈；B项heavyweight(重量较重)，所以错；D项的意思“重量轻、容易被塑成不同的形状，但容易生锈”，所以D项错。
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