Intonation&Context in English can do this also. Note:
Language came long before punctuation.
My terms are not linguistically correct (maybe theres a better word than raisingtone (or ^) to use here in reference to ENG speech, i don't know)
What is a question but a statement with a request attached. a request for more details, for acknowledgement, for agreement, for validation, for the other persons thoughts, etc....
- You work at the bank (neutral tone - statement)
- You work at the ^bank^ (tones rises at the end - question)
You work at the (pause) bank (pause shows disbelief, or lack of understanding, while the statement on a whole shows full comprehension, thus a rhetoric question if you also lowered the tone of Bank it would imply that the location is the part being questioned where as if you raised or lowered tone on You or Work it would indicate more nuisance to the question)
John's here (statement)
- John's ^here^ (question made from whole statement via raising the tone on here)
- ^John's^ here (questioning specifically that John is the one who is here (as though john was not expected or undesired a contrast) by raising the tone on john
a lot of ways to make questions out of statements just by changing the tone in ENG and in Korean as well, which I noticed you are also studying, can have the statement be a full question on it's own context dependent.
It is not uncommon across many languages particularly colloquially for questions to be formed as is (the statement can be unchanged becoming a question) with some aspect of querying attached ... whether thats a yes/no marker like latin -ne or hindi kya or the amazing variance of korean endings that can alter the verb to mean number of type of questions (separate from the question word itself) .... it is FAR more common with yes/no questions though and obviously theres way more ways to ask a question in each language that has this feature.
Elsewhere, yes-no questions without the -ne suffix were marked wrong. I thought the suffix was optional if the sentence was pronounced in the rising intonation indicating it was a yes-no question. Then, someone commented and told me that it was not optional. Now, this sentence from Duo comes without -ne. I'm at a loss.