I got nailed for translating it as What time do you close? instead of "At what time..." Really?
LOL and here it is FOUR YEARS LATER and it hasn't been fixed. Reporting it although honestly I don't know why.
What time do you close is perfectly acceptable. Too inflexible, Duolingo!
This (the superfluous use of "at") was reported in 2014. Yet four years later, nothing has changed. I guess it's true that with AI there is truly nobody home.