单项选择题
Given the following six method names：（1）addListener（2）addMouseListener （3）setMouseListener（4）deleteMouseListener（5）removeMouseListener（6）registerMouseListenerHow many of these method names follow JavaBean Listener naming rules？（）
A.1 B.2 C.3 D.4 E.5
多项选择题 Which two methods， inserted independently at line 17， correctly complete the Sales class？（）
多项选择题 Which two are true？（）
多项选择题 Which three are valid？（）
