behavioral adaptation happens when a creature makes changes to adapt and to survive in its changing environement (through microevoltion). normally chanes to help survive and it not life threating so that it can adapt without dying
let's mark out the options
A. marks its territory with its scent
this does not help it survive so this is not the answer
B. artic fox has thick fur on its feet for warmth
this is for survival and could have been adapted so this could be the right answer
C. hummingbird has long bill to reach flower
probably not becasue if it didn't have the bill it would die from lack of food before it could adapt
D. egret has long legs for wading in the mud
I am not an expert of egrets and do not think that this helps for survival much
so I would say the answer is B