A:元素R位于周期表中第ⅤA族
B:RO3﹣中的R只能被还原
C:R2在常温常压下一定是气体
D:若1 mol RO3﹣参与该反应,则转移的电子的物质的量为5 mol
英国有深色和浅色两种桦尺蛾,它们都栖息在树干上.当树林周围变成工厂后,两种桦尺蛾的数量发生了变化,如图所示,引起桦尺蛾数量变化的根本原因是( )
——I can hardly believe my eyes. Is that you, Lucy?——Yes. It has been almost 20 years______ we were together.