Which of These Is Not an Adaptation of Animals Living

Which of these is not an adaptation of animals living in the arctic tundra?

A) Small mouse-like lemmings make tunnels and burrows under the snow or ground.
B) The musk ox grows a thick coat to conserve heat.
C) The chicken-like ptarmigan burrows in the snow during the storms.
D) Polar bears change their fur coat color from white to brown (with the seasons) .
E) Caribou and reindeer migrate to and from the tundra.