81÷9=9(m)
9×4=36(m)答:正方形的周长是36厘米
下列关于点电荷的说法,正确的是( )
-_________ weather it is! We can't go boating on the Xuanwu Lake.
-Don't worry. Let's go to the Science Museum instead.
任选一题,完成作文。