Same question; different answers
The Gospel of Luke describes God responding differently to different kinds of questions and doubts. In chapter one, an angel announces to Zechariah that he and his wife Elizabeth will become the parents of John the Baptist. In light of his advanced age, Zechariah doubts the angel's message and asks 'how can I know this is true?' In response, he gets a sign: the angel strikes his tongue so he cannot speak.
In the same chapter, Mary is told by an angel that she will give birth. In light of her virginity, she is confused. She asks 'how can this be true?' This is almost exactly the same question Zechariah asked; yet, instead of being struck dumb, the angel grants her a detailed explanation.
I can only figure that the reason for the different angelic responses was due to the spirit of the questioners. Zechariah probably doubted the angelic proclamation; whereas Mary probably didn't doubt, but failed to understand.
Jesus also responds differently to different types of questions and doubts. When his critics and enemies ask him to produce a sign, wonder, or miracle, he refuses to give them one. Yet when one of his own disciples says 'I will not believe in the resurrection unless I can put my fingers in his wounds,' Jesus allows him to do just that.
Within apparently very similar questions, I see a spectrum of attitudes, and it appears that these attitudes determine the type of answer one receives from God.