Which of the following is a common sign of croup?

A barking cough is a classic and characteristic sign of croup, which is an upper airway infection often seen in children. This type of cough resembles the sound of a seal barking and is a result of inflammation in the larynx, trachea, and bronchi. The inflammation narrows the airway, leading to this distinctive cough that can become worse at night.

While high fever, rapid heart rate, and chest pain may be associated with other medical conditions, they are not typical signs of croup. High fever can occur with many viral infections but is not specific to croup. Rapid heart rate may also arise in various illnesses but does not distinguish croup. Chest pain is not a common symptom in croup and may indicate other issues that require different evaluation and treatment. Therefore, the barking cough is the most definitive and common sign of croup that aligns with the clinical presentation of this condition.