Teacher: Why are the days longer in summer and shorter in winter?
Student: During summer ,heat expands,and in winter, cold contracts.Therefore, the days are long in summer and short in winter.
学生：夏天热胀，冬天冷缩，所以夏季天长，冬季天短。
Summer And Winter
学生：夏天热胀，冬天冷缩，所以夏季天长，冬季天短。
