What do Scrooge's repeated questions achieve?

The beginning of the story shows Scrooge very much in control of his life and even of those around him. He uses his money to control others, and when the spirits arrive, for the first time we see him out of control. Him asking questions helps the reader to see just how out of control he is, as well as how vulnerable he feels when he is out of control.

Although he asks questions of all of the spirits, we see him the most vulnerable with the Ghost of Christmas Future, who refuses to speak and answer his questions. This is disconcerting for Scrooge, and the more he asks and does not receive an answer, the more agitated and anxious he gets.

"'Before I draw nearer to that stone to which you point,' said Scrooge, 'answer me one question. Are these the shadows of the things that Will be, or are they shadows of things that May be, only?'

Still the Ghost pointed downward to the grave by which it stood. 'Men’s courses will foreshadow certain ends, to which, if persevered in, they must lead,”'said Scrooge. 'But if the courses be departed from, the ends will change. Say it is thus with what you show me!'

The Spirit was immovable as ever."

Dickens' use of questions makes the most sense because Scrooge is in an unfamiliar situation throughout the night with all of the ghosts, and with the final ghost, he is the most scared. His natural reaction is to ask questions, and this helps the reader to better understand him.