Here the complete list of answers:
- Y: yes (Default)
- n: no
- a: yes to this question and all others (or always yes).
- x: abort (exit)
- d: show the differences between the old and the new file
- h: help, list all options
So if you don't remember this definitions you can always enter h and see the list. Also in the new version, when you enter one of the letters you will see the definition showing behind the question.
The one in uppercase is the default one. If that is your choice, you can just hit enter.