计算(-3a2)2的结果是( )
A.3a4
B.-3a4
C.9a4
D.-9a4
(-3a2)2=32a4=9a4.
故选C.
地轴与黄道平面的夹角为
A.23°26′
B.66°34′
C.90°
D.随季节变化
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