TWO： 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?
John：Well ，in the summer the days are long，and in the winter the days are short.
老師：我們都知道熱脹冷縮的道理�，F(xiàn)在，誰(shuí)給我舉個(gè)例子？
約翰：嗯，在夏天天都長(zhǎng)，在冬天天都短。