One day you meet three persons, each either a Knight or a Liar. You ask "How many of you are knights?", and the first person answers "Grok!".
Not understanding, you ask the second one "What does 'Grok' mean?", and he answers "One", but then the third one cries out "That's false!".
What can you tell about each person, if anything?
(In reply to solution
I agree "B" must be a Liar, and "C" a Knight, but "A" could be a Liar if "grok" meant "zero" or "three", for example.
Thus, you cannot tell what "A" is.