A question is a great way to use as the hook of an essay. Starting with a question about is a great way for the reader to want to learn more about your topic. Good questions to hook a reader is; "Could it be ......?", "Why is it .......", "Did you ever know .......", and "Have you ever hear of ......"
The answer is 'his hair turns grayer' - that is the physical change which took place in the spirit of Christmas present from when he first appears in the story to when he leaves.
