"This is the engineer's cat."
Translation:هٰذِهِ قِطّة اَلْمُهَنْدِس.
Report it. I'm not sure what the contributors had in mind when they added this sentence to the database, but anyway both words should be correct unless the gender was specified in the English version, since قطة is female cat and قط is male cat. Or maybe Duolingo is showing "typo" message because the diacritics were not written (just guessing since I do get such message when I do German and I answer without using umlauts).