下列图形中，既是中心对称图形又是轴对称图形的是（   ）

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    The Spring Festival is the Chinese New Year's Day. It usually 1 in January or February. Everyone in 2 likes the Spring Festival very much. When Spring Festival comes, I usually 3 my parents clean our house and do some 4.  5   that day,  6 eats 7, New Year's cakes and some other food. But I 8 dumplings best. We usually 9 dumplings and  10  TV. I like the Spring Festival.

已知 ${\left(x-\frac{1}{x}\right)}^n$的展开式中第3项与第6项的二项式系数相等，则展开式中系数最大的项为第（　　）项．

阅读下表（表中之数字，表示各时代在各区域中治水事业活动之次数）。据此无法推论的是（    ）