"The girl is wearing a blouse."
Translation:Το κορίτσι φοράει μία μπλούζα.
Again, this is a matter of correctly typing answers in.
A lot of people send in reports suggesting that their answer should be accepted, while they use the wrong article. For example, if you type "Η κορίτσι", it will be marked as incorrect, because the correct article is το, and not η.
But Duolingo will suggest that the correct translation is "η κοπέλα" and not "το κορίτσι", because you used the article η, and there is a correct alternative with that article. Long story short, it doesn't mark the article wrong, but the actual noun following the article you picked.
Please make sure that you typed everything in, correctly. ^.^