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Teacher: We all know that heat causes an object to expand an cold cauese it to contract. Now, can anyone give me a good example? John: Well, in the summer the days are long, and in the winter the days are short. 老师：我们都知道热胀冷缩的道理。现在，谁给我举个例子？ 约翰：嗯，在夏天天都长，在冬天天都短。 | 
