You change keep it the same I think, the question is pretty confusing though
The correct indefinite article for the noun <em>veste</em> would be une
On the teeth brushing one it should be Te cepillas
“In the future”
So is the first one, “habrán cambiado”.
Explanation:
If you put the 3rd one is wrong because is talking in the present form, like now and not something that is going to happen in the future and that is not what the sentence is stating.
