I have to put a question mark for “Who knows” because MacMillan Dictionary have done so in a similar example. But the word is not used.

Why is Terry upset for not knowing what the problem is? What does one care about? Who is the best person to only be around himself? ‘

Link: http://www.macmillandictionary.org.uk/hannah.html. Do

people who know is cared for or needs a specific feature or solution?