Final answer:
Infants less than 6 months old are at risk for hypothermia because they cannot shiver and rely on nonshivering thermogenesis through the breakdown of brown adipose tissue.
Step-by-step explanation:
A child less than 6 months of age cannot shiver; therefore, the child is at risk for hypothermia. Shivering is an important response to cold that generates heat in the human body. Since infants have an underdeveloped thermoregulatory system, they rely on nonshivering thermogenesis, which is the breakdown of brown adipose tissue or brown fat. This brown fat, which is particularly valuable for temperature control, is distributed over the back, chest, and shoulders of newborns. However, if an infant is exposed to cold for extended periods and their brown fat reserves are exhausted, they lack the shivering mechanism as a backup to produce warmth, which can lead to hypothermia, a potentially dangerous drop in body temperature.