Translation:It is natural that you become independent.
What is wrong with "it's natural for you to become independent"? This is how I'd normally say it in English.
My answer "It is natural that you are becoming more independent" was not accepted. Duo wants "... that you become ...".
However in another exercise in this batch the sentence "She doubts that we are becoming more popular" is translated by Duo as "Elle doute que nous devenions plus populaires". So the Subjunctive Present of devenir can equally be translated as "becomes" or "are becoming". I think this indicates that there is nothing wrong with my reply and that Duo is missing a correct answer here.
You would need the French sentence to be "plus indépendant" for that to work.
Next to the button for "discussion" which brings you into this forum, there is a little flag for "report". When you go into that, it gives you a number of options, the last one of which is "my answer should be accepted". I have reported a number of things, but usually check on the discussion forum first to see if other people can throw any light on it.
I have often found that duolingo rejects perfectly correct "free translations" that would be used and understood by English people in favour of rather stodgy littoral word by word translations that would probably only be used by people whose mother tongue is not English.In most cases the only way to progress rapidly through a lesson is to use such word by word littoral translations that you would never use in practice.This is frustrating,but is a price to pay when using a free system which is not programmed to accept all possible correct answers.This has become very apparent in this section dealing with the use of the subjunctive tense.
They do a terrible job of translating the subjunctive. It's worse than any other section I've seen.
Because of "il est naturel que".