The big problem with duoLingo is that lots of correct answers get rejected. There are so many correct ways to translate this in English, and most of them don't count as correct. After a while you end up having to memorize the possible answers duoLingo will accept.
Also "The person who listens to" - especially since it's in their own dictionary hints!! Sometimes these terms are a little difficult to translate, so I look at their hover hints to play it safe, and then get rejected. Frustrating.