Teacher：We all know that beat causes an object to expand an cold cauese it to contract.Now,can anyone give me a good example?
老师：我们都知道热胀冷缩的道理.现在,谁给我举个例子?

John：Well ,in the summer the days are long,and in the winter the days are short.
约翰：嗯,在夏天天都长,在冬天天都短.