回答下列问题：
排序。
A. There are five books on the table.
B. It's small, but it's clean.
C. There is a doll on the bed.
D. Look! This is my room.
E. I like my room.
F. There is a table and a bed in my room.
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元旦放假3天，家住广东深圳的高中生肖军一家去北京旅游，肖军妈妈发现北京比深圳天黑的早。肖军同学应该从哪些方面给妈妈解释产生该现象的原因（ ）
