A: NaOH的固体保存
B: 用天平称取NaOH固体
C: 加水溶解氢氧化钠固体
D: 将配好的溶液装瓶存放
已知⊙O1半径为3cm,⊙O2的半径为7 cm,若⊙O1和⊙O2的公共点不超过1个,则两圆的圆心距不可能为( ).
欧洲人酷爱食用____ 和 ____ ,这与本区发达的____ 业有密切关系.
— Did you study any other languages English when you were at college?
— Yes, I studied three. But I have forgotten all a few words of each.