Which of the following can be a sign of increased work of breathing?

Nasal flaring is a physiological response that indicates increased work of breathing, particularly in children and infants. It occurs when the nostrils widen during inhalation, which helps to improve air intake when individuals are experiencing difficulty breathing. This response is a result of the body attempting to increase airflow into the lungs, especially when there is an obstruction or distress in the respiratory system. It is a visual sign that healthcare providers look for during assessments of respiratory distress.

Increased appetite, fatigue, and clear skin do not indicate increased work of breathing. Increased appetite may suggest physiological well-being or an energy surplus, while fatigue can result from various causes but is not a direct indicator of respiratory effort. Clear skin, likewise, relates to general health rather than respiratory function. Therefore, nasal flaring is distinctly associated with the body's need for more oxygen and its efforts to enhance respiratory efficacy, making it the correct choice in this context.