A:高尔基
B:郭沫若
C:鲁迅
D:列夫·托尔斯泰
H+____; OH﹣____; CO32﹣____; Cl﹣____; SO42﹣____;NH4+____.
如图所示,用细线通过轻网兜把质量为m=0.5kg的足球挂在光滑墙壁上(细线延长线通过足球球心)。已知悬点到足球球心的距离为L=0.5m,足球的半径为R=0.3m,重力加速度为g=10m/s2,求:
As the smallest child of his family, Alex is always longing for the time _______ he should be able to be independent.