"Is this the second largest city in Vietnam?"
Translation:Đây là thành phố lớn thứ hai ở Việt Nam?
I'm not entirely sure what makes this a question.
If someone said to me "Đây là thành phố lớn thứ hai ở Việt Nam" I would see it as a statement i.e. "This is the second largest city in Vietnam" rather than "Is this the second largest city in Vietnam"
Yep, I'd agree that sounds like the case for the vietnamese sentence you've written. In my app-version, the sentence also had an "ư" at the end of it, so I assumed/guessed that turned it into a question?
Still, I'm not sure if what you saw had this because sometimes I get the impression different users are seeing different question/answer pairings? (Judging from some of the past posts I've seen from others). Does Duolingo inject a bit of randomness into its q/a pairings? I.e. since each q can have multiple potential variations of answer and vice versa, does duolingo randomly pick a preferred pair?
What makes this a question is the rising tone for "Nam" even though it really doesn't have one. Just like the rising tone in English makes it an obvious question. But what if last word did have a rising tone, do you make it even higher somehow?
Am I on the right track?