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zui nan duan de da lu nan ji zhou ( xia )
Author(s): 
Pages: 4-5
Year: Issue:  3
Journal: Required Reading for Junior Middle School Students

Abstract: <正>独特的昼夜地球的自转产生了昼夜交替现象,地球的公转又产生了一年四季。在一天中,白天和黑夜的时间是随季节的转换而不断变化的。但不论如何变化,在24小时里,总会有白天和黑夜交替出现。南极独特的地理位置,演化出
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