A.当单击按钮Command1时, Command2和Command3按钮不可用
B.当单击按钮Command1时, Command2和Command3按钮不可见
C.当单击按钮Command1时, Cammand2按钮不可用和Command3按钮不可见
D.当单击按钮Command1时, Command2按钮不可见和Command3按钮不可用