Are lúc, vào lúc and vào all accepted to express time?
and throughout this lesson, sometimes "at what time" is not accepted...
I will review all the skill tree and add this answer.
Also, what’s up with the Tips & Notes? It has only one word for some reason.
That's how it should be ... because Duolingo is so great :P
In English we usually say " when" rather that "at what time"
"When" and "what time" are pretty much interchangeable.
"when" is marked as incorrect although that is the more usual expression.
Just another great example