Suppose that the dam on Lake Whitney closed on 6/3/98.  Which of the following variables would be appropriate for representing this event?  Select ALL appropriate variables.
1
'Lake Whitney's dam', with values [changed from open to closed, changed from closed to open]
'Lake Whitney's dam', with values [true, false]
'State of Lake Whitney's dam', with values [open, closed]
'State of Lake Whitney's water', with values [rising, falling]