单项选择题

阅读下列代码片段
class InterestTest______ActionListener
public void actionPerformed(ActionEvent event)
double interest=balance*rate/100;
balance+=interest;
NumberFormat format=NumberFormat. getCurrencyInstance();
System. out. print]b("balance="+formatter. format(balance));

Private double rate;

在下画线处，应填的正确选项是______。