Which of the following is an optional method of heat production in infants?

Shivering is indeed considered an optional method of heat production in infants, but it is not a primary or typical mechanism for them. Infants possess a limited capacity for shivering as they are still developing their ability to control muscle contraction for thermogenesis effectively. Instead, they primarily rely on non-shivering thermogenesis, which is an efficient process involving brown adipose tissue that generates heat in response to cold temperatures without muscle contractions.

In understanding thermoregulation, it's important to recognize that infants have alternative mechanisms to maintain their body heat, such as non-shivering thermogenesis, resting metabolic functions, and even voluntary muscle activity to some extent. However, shivering is not a dominant or common method in neonates, as it is during later stages of life. For this reason, it is categorized as an optional method rather than a primary mechanism of thermogenesis in infants.