Final answer:
The amount of body fat on their bodies is the main factor that impedes premature babies from effectively regulating their body temperature because it provides essential insulation.
Step-by-step explanation:
The major factor that most impedes premature babies from regulating their body temperature is b. The amount of body fat on their bodies. Premature infants have less body fat compared to full-term infants, which means they lack adequate insulation to maintain their body heat. Body fat is essential for thermoregulation because it helps to conserve heat by providing insulation. Since premature babies have not had sufficient time to develop this crucial layer of fat, they are more susceptible to hypothermia and require specialized care to ensure their body temperature remains stable.