The dissolved oxygen content in water
I might be wrong but I think C ( what the wave it traveling through). I think C because a wave medium is the substance that carries a wave (or disturbance) from one location to another. The wave medium is not the wave itself and it doesn’t make the wave. It just Carries or transports the wave from its source to other locations.
My favorite animal is the Arctic fox it has very small ears because with big ears very much heat is lost so the small ears cause the fox to lose less heat.
The innermost cells of the epidermis are continuously dividing through mitosis to form new cells. The newly formed cells move up through the epidermis toward the skin surface, while producing a tough, fibrous protein called keratin.