Final answer:
Among the given options, 'inefficient metabolism' does not make infants and children more prone to hypothermia because a more efficient metabolism would actually help in generating heat, not losing it. Instead, small muscle mass, little body fat, and a large body surface area all contribute to increased risk of hypothermia.
Step-by-step explanation:
The question asks which of the following does not make infants and children more prone to hypothermia: small muscle mass, little body fat, inefficient metabolism, or large body surface area.
Factors that contribute to making infants and children more prone to hypothermia include small muscle mass which limits heat production through shivering, little body fat which provides less insulation, and a large body surface area relative to their body mass which leads to more rapid heat loss compared to adults. However, the statement 'inefficient metabolism' does not make sense in this context since a higher metabolic rate, or more efficient metabolism, increases heat production and would help prevent hypothermia.
Newborns have a method for generating heat called nonshivering thermogenesis, which involves the breakdown of brown fat. This specialized fat helps to insulate and generate heat in infants. Therefore, 'little body fat' as a choice might be confusing without clarification, because while overall body fat does contribute to insulation, brown fat is actively used for heat generation in infants.