This answer only makes sense if you are , for example, a pest control officer who is treating an outbreak of something and is reporting back to head office. A student will always be AT a university, never IN a university (and no comments about students never being in university either!!). I know Duolingo has some very weird phrases in this course - 'who are you father' or 'a cow and a friend' - but this is just so far away from being a phrase you will ever need/use/ see again... bonkers. Ah well, na gabh dragh. Co sibhse, athair? Bo no caraid?
Listen, ive written the correct answer for English grammar a hundred times now. You can only be AT university in English. Your question is wrong. Change it. It's maddening. I refuse to be "in university" because you cannot be "in university" in Englisn, even if that is the correct preposition in Gaelic. Its just wrong. Change fhe correct answer to thr question. Im tired of entering the correct answer to be told it js wrong. Ive done it over a hundred times now and cannot progress.
In Canada we say both "in" or "at" university, pretty much interchangeably. The same way we say one is located in Nova Scotia or recovering in the hospital, one is studying in university. You could say "at" but "in" is perfectly acceptable and more common, at least where I live. If you are mentioning a university by name, you might say "I'm at Dalhousie University".