Question Mark Meaning

Example : The punctuation mark “?”, used at the end of a sentence to indicate a question.  There’s a question mark over whether or not he’ll be fit for the next game.2011 April 11, Phil McNulty, “Liverpool 3 - 0 Man City”[1], BBC Sport:  Dirk Kuyt sandwiched a goal in between Carroll's double as City endured a night of total misery, with captain Carlos Tevez limping off early on with a hamstring strain that puts a serious question mark over his participation in Saturday's FA Cup semi-final against Manchester United at Wembley.