sentences: if a living thing becomes too cold then that living thing will die & keeping warm is the opposite of becoming cold ->  an animal usually requires warmth for survival  an animal usually requires warmth for survival & if the environmental temperature is too cold then an animal in that environment may become cold ->  an animal requires warmth in cold temperatures  an animal requires warmth in cold temperatures & thick fur can be used for keeping warm ->  thick fur can be used by animals for survival in cold temperatures  thick fur can be used by animals for survival in cold temperatures & winter has cold temperatures ->  thick fur can be used by animals for survival survival during winter  thick fur can be used by animals for survival survival during winter & a bear is a kind of animal -> thick fur can be used by bears for survival during winter