Please select only one option. If it won't allow you to register for the discussion time, it is because the session is full. Please register for the waitlist and we will let you know if space opens up. If you wish to revise your selection, you need to "UNSELECT" your first selection, and "RESELECT" your revised selection.
Yes, that means you need to "click again" on your previous selection in order to turn off the radio button. Then click on your new selection. Then submit
If your plans change, and you need to cancel or change your selection, your receipt will have an "edit submission" link.