Which of the following is a signal that a person may be experiencing breathing difficulties?

The signal indicating that a person may be experiencing breathing difficulties can be observed when they look in pain and have noisy breathing. Pain may be a sign of respiratory distress, and noisy breathing can indicate various issues, such as wheezing or stridor, which are often associated with obstructions or inflammation in the airways.

In contrast, appearing relaxed and calm, showing a steady respiratory rate, and speaking in full sentences typically suggest that the individual is not experiencing any significant breathing difficulties. A steady respiratory rate often falls within the normal range, while being able to speak in full sentences generally indicates adequate airflow and oxygenation. Therefore, the presence of pain and noisy breathing is a clear red flag for potential respiratory problems.