题目

下列各项说法或比较中正确的是A．氧化性：Ag+ >Cu2+ >Fe3+  B．酸性：HI>HCl>CH3COOH>H2CO3C．主族都含非金属元素，副族都为金属元素D．一种元素可形成多种离子，但只有一种原子 答案：BThe instant Nate woke up the next morning, he saw a note on the bedside table _____ by his wife_______ “Breakfast is ready. Have a nice day. A．left; saidB．leaving; sayingC．left; sayingD．leaving; say