Final answer:
The first sign that an infant is cold can be an increase in physical activity (a). Other signs may include mottled skin, and infants uniquely generate heat through nonshivering thermogenesis involving brown adipose tissue. The Apgar score is used to assess an infant's condition at birth.
Step-by-step explanation:
If an infant is cold, the first signs exhibited can include an increase in physical activity or rapid movements in an attempt to generate heat, which is a natural response to a decreased body temperature. However, initially, infants might also show other signs such as mottled skin due to constriction of blood vessels in the skin. As a method to regulate temperature, newborns undergo nonshivering thermogenesis, which involves the breakdown of brown adipose tissue, a process unique to infants.
The condition of the infant is often assessed using a scoring system known as the Apgar score, which includes five criteria: skin color, heart rate, reflex irritability, muscle tone, and respiration. Signs and symptoms of a baby in distress due to problems like temperature instability might also include apnea, bradycardia, or difficulty feeding.