谁有高一英语辅导报暑假自测题(一)(二)(三)答案

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 (浸) 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 becomes. Annealing can also be used on other material, such as glass.
1. Annealing can make metal .
A.hardand tough(韧) B. hard but brittle C. soft but tough D. soft and brittle
2. Why do people put hot metal in water?
A.Tomake it hard B. To make it soft. C. To make it cool. D. To make it brittle.
3. In annealing, the required hardness of a metal depend on .
A. the quantity of water used B. the temperature of the me