If you could meet in person any SF/F author, living or dead, who would it be? And if you could only ask one question of this author, what would it be and why?

John Ottinger at Grasping for the Wind asks:
If you could meet in person any SF/F author, living or dead, who would it be? And if you could only ask one question of this author, what would it be and why?
I’m a shy-with-strangers sort of person, so I haven’t met many authors, SF or otherwise.
But let’s pretend that handicap isn’t there.
So many choices…but for amusement, I will pick the late Isaac Asimov, and I would ask him this, given his prolific writing, both fiction and non fiction:
Is there any subject that you don’t think you could write a book on?