digs up food walks in deep snow climbs rocky cliffs runs under bushes
I gave my students this multiple choice question: A bird called a ptarmigan has feathered feet. The feathers on the feet of the ptarmigan are most helpful when this bird ___.

Only one answer is correct among these 4 choices:
- digs up food
- walks in deep snow
- climbs rocky cliffs
- runs under bushes

Could you tell me which one is correct?

walks in deep snow