Answer:
I believe that it is D.
Explanation:
If ice caps are melting, and polar bears use the ice flows to get their food, then the polar bears can't use the ice to get food. so, the polar bears most likely are expanding their diets to adapt to their surroundings. So, polar bears are probably moving off the sea ice and eating other foods.
The myelin sheath is the layer of fat cells that insulates most axons and speeds up the transmission of nerve impulses.
The answer would be fats and proteins.
The answer should be altitude