Agreed, but let's not forget this is not a face to face classroom. These sentences have been programmed into a computer program. So, if by chance, or by intent, something was not included the program will mark it as incorrect. When I say by intent I mean that Duo could not possibly include every regional and colloquial version of the languages.
In this case of course, it is good English. Try reporting it tohelp out other learners. See here for some tips etc but most important the Guidelines: