（7分）如图，将铜片和锌片焊接在一起组成A电极，B为碳棒进行电解实验，电解液中含硝酸银和硝酸铜各0．1 mol。已知电路中通过0．2 mol电子。

（1）请写出A．B两极发生反应的电极反应式A：        B：          

（2）请分析A．B两极质量变化情况为A：___________B：__________  

There ____ a table, four chairs, three bikes in the courtyard, in the  middle of which ____ two tall trees with great shade.

A．are; is

B．is; are

C．has; have

D．have; has