whats the name of book 4 of avatar the last airbender?

answers1: air <br>
what is airbender?
answers2: I' don't think theres gonna be book 4. Because in book 3 it
will be Aang's final battle. Unless if nickelodeon gives it a twist
answers3: sorry, there's no book 4.
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If there was, it would probably be air but what would be the story?
aang learns waterbending in bk1, earth in bk2, and fire in bk3. He
already mastered air.
answers4: air. The book names fallow the cycle of elements from which
the avatar is born. In the show he starts with air,but then learns
water and so on, so the cycle goes like this: water, earth, fire, air,
water... and so on and that's how you get the names for the books