假设月亮绕地球作半径为R的匀速率圆周运动，则月亮的运动周期正比于()
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与传统的沥青防水卷材相比，氯化聚乙烯防水卷材的主要特点有哪些？最适宜用于哪些防水工程？
材料内部孔隙尺寸大小、形态特征对材料性能有什么影响？
Shortly after the author left home one evening, she discovered that ______.
A. her son had brought his girlfriend home
B. her son had left home with his girlfriend
C. she shouldn’t have completely trusted her son
D. she should have taken the children along with her
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