Radio Buttons

  Just as you can play only one station on a radio at a time,
  a radio button allows you to activate only one setting from
  two or more settings.  A radio button is the diamond-shaped
  button next to a setting.

  A setting with a highlighted radio button next to it is the
  activated setting.  To change the activated setting, move the
  pointer to the button next to the setting you want to activate
  and click MB1.  This setting now contains the highlighted
  radio button.