参考答案：D

解析：Tendency toward capillary fragility has nothing to do with thermoregulation. The hypothalamus is the site of temperature regulation. In preterm neonates, the CNS is poorly developed, so these neonates may be more prone to temperature instability. The large skin surface area provides the perfect medium for heat loss through evaporation and convection. Lack of S. C. and brown fat are also contributors to temperature instability. Without S. C. fat, there is nothing to insulate the infant from heat loss. Brown fat provides calories that help with heat production.