As long as I can remember, ___________I called, his wife would answer the phone.
铜离子____,氟元素____,3N2O5表示:____,氧化镁中镁显+2价____.
如图中的正方体、圆柱和圆锥底面积相等,高也相等.下面哪句话是正确的?( )
下列说法错误的是( )