How many feats/skills/powers can a player retrain on gaining a level?

Question

Every time your character gains a level, you can retrain. To do so, change one of the following: a feat, a power, or a trained skill. You can make only one change per level.

I believe that means one change when gaining a level but it could be interpreted as one change per level when gaining a new level (eg. when gaining 5th level you can make 4 changes, one on each level had).

Answer 1

One

Your first interpretation is correct, it's one change each time you gain a level.