In earlier lessons we learned that кіт means male cat. So when I have specified 'male cat' in my answer, should not that be approved as correct?
As there are no different words for female and male cat in English, you should use just "cat".
Bearing in mind that we can use "кіт" in the back translation, as it is often used by default when we do not know cat gender.
Wait- does 'odna' mean this was a female mouse?
"Миша" is a feminine noun (independently of the actual gender of the concrete animal you are talking about).