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는지? i see it at the end of a sentence to make a question ending?

It would be easier to answer if I saw the full sentence. Generally, we can think that the sentence omits a verb "궁금하다(Wonder)", "알고싶다(want to know)", or anything associated with the feeling of "Get information". "는지" can be translated into "whether". For example, "나는 네가 공부하고 있는지 궁금하다(I wonder whether you are studying)". However, if you say so in a real conversation, it would sound a little weird and may make other people confused. Hope this will help you understand it.