Which of the following is a sign of respiratory distress in children?

Clammy, moist skin is a sign of respiratory distress in children because it can indicate a physiological response to poor oxygenation and increased effort in breathing. When a child experiences respiratory distress, their body may activate sweat glands as part of the autonomic nervous system's response to stress, leading to clammy skin.

In addition, respiratory distress often is accompanied by a lack of adequate ventilation, which can lead to issues such as cyanosis or increased heart rate, further enhancing the child’s sympathetic nervous system response. This physiological state might cause perspiration in an attempt to regulate core temperature and manage oxygen levels in the bloodstream.

The other choices are not indicative of respiratory distress. Excessive smiling and a calm demeanor suggest that the child is comfortable and not in distress. Consistent normal breathing indicates that the child’s respiratory system is functioning well, without signs of obstruction or distress. Each of these aspects contrasts with the signs indicative of respiratory difficulties, where children typically display anxiety, discomfort, and abnormal skin conditions.