How Many Radio Buttons Can Be Selected at the Same

How many radio buttons can be selected at the same time as the result of the following code?
Hours = new JRadioButton("Hours") ;
Minutes = new JRadioButton("Minutes") ;
Seconds = new JRadioButton("Seconds") ;
Days = new JRadioButton("Days") ;
Months = new JRadioButton("Months") ;
Years = new JRadioButton("Years") ;
TimeOfDayButtonGroup = new ButtonGroup() ;
DateButtonGroup = new ButtonGroup() ;
TimeOfDayButtonGroup.add(hours) ;
TimeOfDayButtonGroup.add(minutes) ;
TimeOfDayButtonGroup.add(seconds) ;
DateButtonGroup.add(days) ;
DateButtonGroup.add(months) ;
DateButtonGroup.add(years) ;

A) 1
B) 2
C) 3
D) 4