Annealing is a way of making metal softer by heating it and then letting it cool very slowly. If metal is heated and then cooled very quickly , for example by dipping it in water , it will be very hard but also very brittle(脆)---that is , It will break easily. Metal that has been annealed is soft but does not break as easily . It is possible to make metal as hard or as soft as is wished, by annealing it. The metal is heated, and allowed to cool slowly , for a certain length of time. The longer the heated metal takes to cool slowly , the softer it bees . Annealing can also be used on other materials, such as glass.
【小题1】 Annealing can make metal .A．hard and tough (韧) B．hard but brittleC．soft but toughD．soft and brittle【小题2】 Why do people put hot metal in water ? A．To make it hardB．To make it softC．To make it coolD．To make it brittle【小题3】 As suggested by the text , how can glass be made less brittle ? A．It can be heated and then cooled quicklyB．It can be cooled and then heated slowlyC．It can be heated and then cooled slowlyD．It can be cooled and then heated quicklyC
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(答案→)C
解析：文章介绍了一种冶金的方法：annealing（退火）是将工件加热到适当温度，然后进行缓慢冷却，目的是使金属组织更细，更坚硬。
【小题1】细节题：从文章的句子Annealing is a way of making metal softer by heating it and then letting it cool very slowly. 和It is possible to make metal as hard or as soft as is wished, by annealing it.可知金属通过annealing可以变得柔软和坚韧。选C
【小题2】细节题：从文章的句子：by dipping it in water , it will be very hard but also very brittle(脆)可知把热的金属放进水里可以使金属变硬。选A
【小题3】推理题：从文章的句子：The longer the heated metal takes to cool slowly , the softer it bees .可知玻璃也是加热后慢慢冷却可以变得坚韧。选C