There is a subject and its marker in 난 몰라. This implies someone asked you about something pointing at you among several people. And this means his question could be not just a question. He seemed to have some suspicion about you and the situations. This is also true even If there were only two, you and he. And your answer, 난 몰라, might have a hidden connotation that "Others know the truth." But this is not always so.
And 모르겠어 is a plain statement for "I don't undestand."
The Language Level symbol shows a user's proficiency in the languages they're interested in. Setting your Language Level helps other users provide you with answers that aren't too complex or too simple.
Has difficulty understanding even short answers in this language.
Can ask simple questions and can understand simple answers.
Can ask all types of general questions and can understand longer answers.
Can understand long, complex answers.
This answer was given within 60 minutes of the question being posted.
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