It depends on in what scenarios it happened.
To me, in most cases, it refers to B, but it becomes less and less popular in China nowadays. Now we greet with 'how are you?'(怎么样?) or just smile directly.
In some scenarios it could be A especially before meal time.
C only makes sense to me if I'm asking someone or asked by someone in very particular scenario like at home or overtime working after meal time.