It would be ils se promène, I believe, but it could be promèner, check to see if your verb needs to be conjugated.
Answer:
L'éléphant est plus grand que l'ours
Explanation:
We have 2 animals here: "ours" (bear) and "éléphant" (elephant), and we have to do a logical comparison based on their size "grand" (big/tall)
The logical comparison is to say that the elephant is bigger than the bear, that is written "L'éléphant est plus grand que l'ours" in French.
We of course assume both animals are adults in order to have a safe and logical comparison.
