Answer:
b. in cold climates
Explanation:
The warm-blooded organisms living in colder climates have short and round bodies with short appendages to reduce the heat exchange with surroundings and thereby, to stay warm.
The short and muscular bodies of Neanderthal populations, with short arms and legs, would have a higher surface area to volume ratio. The lesser surface area of their bodies with respect to the volume would have helped them to stay warm in cold climatic conditions.