In "A Visit From St. Nicholas," by Clement Clarke Moore, the best way to understand the question and the possible answers is to be sure to first understand what a simile is, and secondly to be aware of the meaning of each of the choices given.
First of all, a simile is a comparison of two dissimilar things that share similar traits, as if they were the same. For example, look at "Her skin was as soft as silk." This is a simile. The comparison is between skin and silk. However, a simile also must use the words "like" or "as" in making the comparison.
In terms of the choices, each seems straightforward: the chimney is an opening in the roof where smoke from the fireplace escapes; the roof is the covering on the top of a house; the hoof is an animal's foot, tough like a deer's horn; and, a reindeer is an animal much like a deer.
If you are confused, there is good reason. I believe this is a trick question. If we study the use of the word "down" in the context of the poem, we will see two important items missing in terms of the definition of a simile:
As I drew in my head, and was turning around,
Down the chimney Saint Nicholas came with a bound.
First, note the absence of "like" or "as." This is our first clue. More importantly, there is no comparison of two things taking place in this segment.
Later in the poem, note the following simile:
...And the smoke it encircled his head like a wreath.
The two things being compared are the smoke and a wreath, which share the same shape. You will also notice that "like" is present in the comparison.
Therefore, your answer should be: none of these.