"Do the students stand up?"
can @duolingo explain why the 느냐 form is not accepted here? In the same section of exercices sometimes both ~느냐 and ~니 are accepted, sometimes only one and I don't seem to see why. According to your own tips: https://www.duolingo.com/skill/ko/Written/tips-and-notes It is said that
When asking a question in 해라체, simply add ~느냐 or ~니 to the verb stem.
So can @duolingo please either explain why only one or the other form should be accepted (or why both)? and at least be more specific in the tips if a difference should be made.