an animal is a kind of living thing & if a living thing becomes too cold then that living thing will die ->  if an animal becomes too cold then that animal will die  if an animal becomes too cold then that animal will die & keeping warm is the opposite of becoming cold ->  an animal requires warmth for survival  an animal requires warmth for survival & if the environmental temperature is too cold then an animal in that environment may become cold ->  an animal requires warmth for survival in cold temperatures  an animal requires warmth for survival in cold temperatures & thick fur can be used for keeping warm ->  thick fur can be used for survival in cold temperatures by keeping warm  thick fur can be used for survival in cold temperatures by keeping warm & winter has cold temperatures ->  thick fur can be used for survival in winter by keeping warm  thick fur can be used for survival in winter by keeping warm & when fur grows it becomes thicker ->  some animals' fur grows thicker for staying warm in the winter  some animals' fur grows thicker for staying warm in the winter & a rabbit is a kind of animal -> a rabbit's fur grows thicker in the winter